next-mdx-remote-client

The next-mdx-remote-client is a wrapper of @mdx-js/mdx for nextjs applications in order to load MDX content. It is a fork of next-mdx-remote.

See some blog applications in which next-mdx-remote-client is used:

• for a demo application which uses app router, visit source code or living web site
• for a demo application which uses pages router, visit source code or living web site
• for a testing application which uses both app and pages router, visit source code or living web site

Why next-mdx-remote-client ?

I started to create the next-mdx-remote-client in line with the mindset of the @mdx-js/mdx in early 2024 considering next-mdx-remote had not been updated for a long time, and finally, a brand new package emerged.

The next-mdx-remote-client serves as a viable alternative to next-mdx-remote having more features.

I would like to highlight some main features:

• It supports MDX version 3.
• It provides well designed components and functions for both "pages" router and "app" router, which completely isolated from eachother.
• It provides internal error handling mechanism.
• It supports import statements and export statements in MDX source, which can be disabled as well.
• Creating table of contents (TOC) is so easy since it supports passing vfile.data into the scope.
• You can get frontmatter without compilng the source while listing the articles/posts via a util getFrontmatter.
• It exports some components and types from @mdx-js/mdx so as you don't need to install.

Let's compare the features of next-mdx-remote and next-mdx-remote-client.

Features	next-mdx-remote	next-mdx-remote-client
support MDX version 3	✅ (as of v5)	✅
ensure internal error handling mechanism in app router	❌	✅
ensure internal error handling mechanism in pages router	❌	✅
support export-from-MDX in app router	❌	✅
support export-from-MDX in pages router	❌	✅
support import-into-MDX in app router	❌	✅
support import-into-MDX in pages router	❌	❌
get frontmatter and mutated scope in app router	❌	✅
get frontmatter and mutated scope in pages router	✅	✅
support options for disabling imports and exports in MDX	✅	✅
support passing vfile.data into the scope	❌	✅
provide utility for getting frontmatter without compiling	❌	✅
expose MDXProvider from @mdx-js/mdx	❌	✅
provide option for disabling parent MDXProvider contexts	❌	✅
expose the necessary types from mdx/types	❌	✅

[!IMPORTANT] You will see a lot the abbreviatons csr and rsc. Pay attention to the both are spelled backwards.

csr stands for "client side rendering" which is related with pages router
rsc stands for "react server component" which is related with app router

General considerations about development

• It is ESM only package
• Needs react version 18.2+, works with latest nextjs ^13.5.6 and ^14.2.4 versions (tested)
• Needs node version 18.17+ as inline with nextjs does
• Vitest is used instead of jest for testing
• Rollup is removed for bundling
• Test coverage is 100%
• Type coverage is 100%
• The parts client side (csr) and server side (rsc) are completely isolated from each other
• Exported a small utility to get frontmatter without compiling the source
• All functions take named parameters
• Supports import statements and export statements in the MDX
• Export statements in MDX work for both app and pages router
• Import statements in MDX work for only app router

[!IMPORTANT] Imported modules in MDX with relative path should be transpiled into javascript before or during build process, otherwise will not work. I believe the community can find a solution to import reqular .jsx or .tsx modules into MDX. With the support of the next/mdx, it is viable to import .mdx into the MDX, but not tested yet.

Installation

This package is ESM only, requires Node.js (version 18.17+).

1npm install next-mdx-remote-client

or

1yarn add next-mdx-remote-client

[!WARNING]
The next-mdx-remote users may follow the migration guide.

The package's exported subpaths

The main entry point / also refers to /csr subpath.

1// main entry point, which is related "pages" router
2import /* */ from "next-mdx-remote-client";
3
4// isolated subpath for the "serialize" function
5import /* */ from "next-mdx-remote-client/serialize";
6
7// sub entry point related with "pages" router
8import /* */ from "next-mdx-remote-client/csr";
9
10// sub entry point related with "app" router
11import /* */ from "next-mdx-remote-client/rsc";
12
13// isolated subpath for the utils
14import /* */ from "next-mdx-remote-client/utils";

The part associated with Next.js app router

Go to the part associated with Next.js pages router

The next-mdx-remote-client exposes evaluate function and MDXRemote component for "app" router.

1import { evaluate, MDXRemote } from "next-mdx-remote-client/rsc";

[!TIP] If you need to get the exports from MDX --> use evaluate
If you don't need --> use MDXRemote

If you need to get the frontmatter and the mutated scope --> use evaluate
If you don't need --> use MDXRemote

Let's give some examples how to use next-mdx-remote-client in "app" router first, then explain the exposed function and component.

Examples for app router

See a demo application with app router, visit source code or living web site

An example with javascript

1import { Suspense } from "react";
2import { MDXRemote } from "next-mdx-remote-client/rsc";
3
4import { ErrorComponent, LoadingComponent } from "../components";
5import { Test } from '../mdxComponents';
6
7const components = {
8  Test,
9  wrapper: ({ children }) => <div className="mdx-wrapper">{children}</div>,
10}
11
12export default async function Page() {
13  const source = "Some **bold text** in MDX, with a component <Test />";
14
15  return (
16    <Suspense fallback={<LoadingComponent />}>
17      <MDXRemote
18        source={source}
19        components={components}
20        onError={ErrorComponent}
21      />
22    </Suspense>
23  );
24};

An example with typescript, parsing frontmatter and providing custom data with scope

1import { Suspense } from "react";
2import { MDXRemote } from "next-mdx-remote-client/rsc";
3import type { MDXRemoteOptions, MDXComponents } from "next-mdx-remote-client/rsc";
4
5import { calculateSomeHow, getSourceSomeHow } from "../utils";
6import { ErrorComponent, LoadingComponent } from "../components";
7import { Test } from '../mdxComponents';
8
9const components: MDXComponents = { 
10  Test,
11  wrapper: function ({ children }: React.ComponentPropsWithoutRef<"div">) {
12    return <div className="mdx-wrapper">{children}</div>;
13  },
14}
15
16export default async function Page() {
17  const source = await getSourceSomeHow();
18
19  if (!source) {
20    return <ErrorComponent error="The source could not found !" />;
21  }
22
23  const options: MDXRemoteOptions = {
24    mdxOptions: {
25      // ...
26    },
27    parseFrontmatter: true,
28    scope: {
29      readingTime: calculateSomeHow(source),
30    },
31  };
32
33  return (
34    <Suspense fallback={<LoadingComponent />}>
35      <MDXRemote
36        source={source}
37        options={options}
38        components={components}
39        onError={ErrorComponent}
40      />
41    </Suspense>
42  );
43}

An example with creating a table of contents (TOC)

I assume you have a MDX file having <TableOfContentComponent /> inside; and you provide some MDX components which have an entry for TableOfContentComponent: (props) => { ... }.

1---
2title: My Article
3---
4# {frontmatter.title}
5
6<TableOfContentComponent toc={toc} />
7
8rest of the article...

You can have a look at an example TOC component in the demo application.

In order to create a table of contents (TOC) I use remark-flexible-toc in the remark plugin list and pass the table of contents objects vFile.data.toc into the scope via the option vfileDataIntoScope. That's it ! So easy !

1import { Suspense } from "react";
2import { MDXRemote, type MDXRemoteOptions } from "next-mdx-remote-client/rsc";
3import remarkFlexibleToc from "remark-flexible-toc"; // <---------
4
5import { calculateSomeHow, getSourceSomeHow } from "../utils";
6import { ErrorComponent, LoadingComponent } from "../components";
7import { components } from '../mdxComponents';
8
9export default async function Page() {
10  const source = await getSourceSomeHow();
11
12  if (!source) {
13    return <ErrorComponent error="The source could not found !" />;
14  }
15
16  const options: MDXRemoteOptions = {
17    mdxOptions: {
18      remarkPlugins: [
19        // ...
20        remarkFlexibleToc, // <---------
21      ], 
22    },
23    parseFrontmatter: true,
24    scope: {
25      readingTime: calculateSomeHow(source),
26    },
27    vfileDataIntoScope: "toc", // <---------
28  };
29
30  return (
31    <Suspense fallback={<LoadingComponent />}>
32      <MDXRemote
33        source={source}
34        options={options}
35        components={components}
36        onError={ErrorComponent}
37      />
38    </Suspense>
39  );
40}

An example with using "frontmatter" and "scope" in JSX in "app" router

1import { Suspense } from "react";
2import { evaluate, type EvaluateOptions } from "next-mdx-remote-client/rsc";
3import remarkFlexibleToc, { type TocItem } from "remark-flexible-toc";
4
5import { calculateSomeHow, getSourceSomeHow } from "../utils";
6import { ErrorComponent, LoadingComponent, TableOfContentComponent } from "../components";
7import { components } from "../mdxComponents";
8
9type Scope = {
10  readingTime: string;
11  toc?: TocItem[];
12};
13
14type Frontmatter = {
15  title: string;
16  author: string;
17};
18
19export default async function Page() {
20  const source = await getSourceSomeHow();
21
22  if (!source) {
23    return <ErrorComponent error="The source could not found !" />;
24  }
25
26  const options: EvaluateOptions<Scope> = {
27    mdxOptions: {
28      remarkPlugins: [
29        // ...
30        remarkFlexibleToc,
31      ], 
32    },
33    parseFrontmatter: true,
34    scope: {
35      readingTime: calculateSomeHow(source),
36    },
37    vfileDataIntoScope: "toc",
38  };
39
40  const { content, frontmatter, scope, error } = await evaluate<Frontmatter, Scope>({
41    source,
42    options,
43    components,
44  });
45
46  if (error) {
47    return <ErrorComponent error={error} />;
48  }
49
50  return (
51    <>
52      <h1>{frontmatter.title}</h1>
53      <p>Written by {frontmatter.author}; read in {scope.readingTime}</p>
54      <TableOfContentComponent toc={scope.toc} />
55      <Suspense fallback={<LoadingComponent />}>
56        {content}
57      </Suspense>
58    </>
59  );
60}

Actually, you may not need to access the "frontmatter" and "scope" in JSX, you can use them within MDX directly, and return just content only.

1// ...
2export default async function Page({ source }: Props) {
3  // ...
4  return (
5    <Suspense fallback={<LoadingComponent />}>
6      {content}
7    </Suspense>
8  );
9}

article.mdx

1# {frontmatter.title}
2
3Written by {frontmatter.author}; read in {readingTime}
4
5<TableOfContentComponent toc={toc} />
6
7rest of the article...

After the examples given, let's dive into the exposed function and component by next-mdx-remote-client for "app" router.

The evaluate function

Go to the MDXRemote component

The evaluate function is used for compiling the MDX source, constructing the compiled source, getting exported information from MDX and returning MDX content to be rendered on the server side, as a react server component.

1async function evaluate(props: EvaluateProps): Promise<EvaluateResult> {}

The evaluate function takes EvaluateProps and returns EvaluateResult as a promise.

Props of the evaluate function

1type EvaluateProps<TScope> = {
2  source: Compatible;
3  options?: EvaluateOptions<TScope>;
4  components?: MDXComponents;
5};

Result of the evaluate function

1type EvaluateResult<TFrontmatter, TScope> = {
2  content: JSX.Element;
3  mod: Record<string, unknown>;
4  frontmatter: TFrontmatter;
5  scope: TScope;
6  error?: Error;
7};

The evaluate has internal error handling mechanism as much as it can, in order to do so, it returns an error object if it is catched.

[!CAUTION] The eval of the compiled source returns a module MDXModule, and does not throw errors except syntax errors. Some errors throw during the render process which needs you to use an ErrorBoundary.

1import { Suspense } from "react";
2import { evaluate, type EvaluateOptions } from "next-mdx-remote-client/rsc";
3
4import { ErrorComponent, LoadingComponent, TableOfContentComponent } from "../components";
5import { components } from "../mdxComponents";
6import type { Frontmatter, Scope } from "../types"
7
8export default async function MDXComponent({ source }: {source?: string}) {
9  if (!source) {
10    return <ErrorComponent error="The source could not found !" />;
11  }
12
13  const options: EvaluateOptions = {
14    /* */
15  };
16
17  const { content, mod, frontmatter, scope, error } = await evaluate<Frontmatter, Scope>({
18    source,
19    options,
20    components,
21  });
22
23  if (error) {
24    return <ErrorComponent error={error} />;
25  }
26
27  /**
28   * Use "mod", "frontmatter" and "scope" as you wish
29   *
30   * "mod" object is for exported information from MDX
31   * "frontmatter" is available even if a MDX syntax error occurs
32   * "scope" is for mutated scope if the `vfileDataIntoScope` option is used
33   */
34
35  return (
36    <>
37      <h1>{frontmatter.title}</h1>
38      <div><em>{mod.something}</em></div>
39      <TableOfContentComponent toc={scope.toc} />
40      <Suspense fallback={<LoadingComponent />}>
41        {content}
42      </Suspense>
43    </>
44  );
45};

If you provide the generic type parameters like await evaluate<Frontmatter, Scope>(){}, the frontmatter and the scope get the types, otherwise Record<string, unknown> by default for both.

[!WARNING] Pay attention to the order of the generic type parameters.

The type parameters Frontmatter and Scope should extend Record<string, unknown>. You should use type instead of interface for type parameters otherwise, you will receive an error saying Type 'Xxxx' does not satisfy the constraint 'Record<string, unknown>'. See this issue for more explanation.

In the above example, I assume you use remark-flexible-toc remark plugin in order to collect the headings from the MDX content, and you pass that information into the scope via vfileDataIntoScope option.

The evaluate options (EvaluateOptions)

All options are optional.

1type EvaluateOptions<TScope> = {
2  mdxOptions?: EvaluateMdxOptions;
3  disableExports?: boolean;
4  disableImports?: boolean;
5  parseFrontmatter?: boolean;
6  scope?: TScope;
7  vfileDataIntoScope?: VfileDataIntoScope;
8};

mdxOptions

It is an EvaluateMdxOptions option to be passed to the @mdx-js/mdx compiler.

1import { type EvaluateOptions as OriginalEvaluateOptions } from "@mdx-js/mdx";
2
3type EvaluateMdxOptions = Omit<
4  OriginalEvaluateOptions,
5  | "Fragment"
6  | "jsx"
7  | "jsxs"
8  | "jsxDEV"
9  | "useMDXComponents"
10  | "providerImportSource"
11  | "outputFormat"
12>;

As you see, some of the options are omitted and opinionated within the package. For example the outputFormat is always function-body by default. Visit https://mdxjs.com/packages/mdx/#evaluateoptions for available mdxOptions.

1const options: EvaluateOptions = {
2  // ...
3  mdxOptions: {
4    format: "mdx",
5    baseUrl: import.meta.url,
6    development: true,
7    remarkPlugins: [/* */],
8    rehypePlugins: [/* */],
9    recmaPlugins: [/* */],
10    remarkRehypeOptions: {handlers: {/* */}},
11    // ...
12  };
13};

For more information see the MDX documentation.

disableExports

It is a boolean option whether or not stripping the export statements out from the MDX source.

By default it is false, meaningly the export statements work as expected.

1const options: EvaluateOptions = {
2  disableExports: true;
3};

Now, the export statements will be stripped out from the MDX.

disableImports

It is a boolean option whether or not stripping the import statements out from the MDX source.

By default it is false, meaningly the import statements work as expected.

1const options: EvaluateOptions = {
2  disableImports: true;
3};

Now, the import statements will be stripped out from the MDX.

parseFrontmatter

It is a boolean option whether or not the frontmatter should be parsed out of the MDX.

By default it is false, meaningly the frontmatter will not be parsed and extracted.

1const options: EvaluateOptions = {
2  parseFrontmatter: true;
3};

Now, the frontmatter part of the MDX file is parsed and extracted from the MDX source; and will be supplied into the MDX file so as you to use it within the javascript statements.

[!NOTE] Frontmatter is a way to identify metadata in Markdown files. Metadata can literally be anything you want it to be, but often it's used for data elements your page needs and you don't want to show directly.

1---
2title: "My Article"
3author: "ipikuka"
4---
5# {frontmatter.title}
6
7It is written by {frontmatter.author}

The package uses the vfile-matter internally to parse the frontmatter.

scope

It is an Record<string, unknown> option which is an arbitrary object of data which will be supplied to the MDX. For example, in cases where you want to provide template variables to the MDX, like my name is {name}, you could provide scope as { name: "ipikuka" }.

Here is another example:

1const options: EvaluateOptions = {
2  scope: {
3    readingTime: calculateSomeHow(source)
4  };
5};

Now, the scope will be supplied into the MDX file so as you to use it within the statements.

1# My article
2
3read in {readingTime} min.

The variables within the expression in the MDX content should be valid javascript variable names. Therefore, each key of the scope must be a valid variable name.

1My name is {name} valid expression.
2My name is {my-name} is not valid expression, which will throw error

So, we can say for the scope, here:

1const options: EvaluateOptions = {
2  scope: {
3    name: "ipikuka", // valid usage
4    "my-name": "ipikuka", // is not valid and error prone for the MDX content !!!
5  };
6};

[!TIP] The scope variables can be consumed not only as a property of a component, but also within the texts.

1my name is {name}
2
3<BarComponent name={name} />

vfileDataIntoScope

It is an union type option. It is for passing some fields of vfile.data into the scope by mutating the scope.

[!IMPORTANT]
It provides referencial copy for objects and arrays. If the scope has the same key already, vfile.data overrides it.

The reason behind of this option is that vfile.data may hold some extra information added by some remark plugins. Some fields of the vfile.data may be needed to pass into the scope so as you to use in the MDX.

1type VfileDataIntoScope =
2  | true // all fields from vfile.data
3  | string // one specific field
4  | { name: string; as: string } // one specific field but change the key as
5  | Array<string | { name: string; as: string }>; // more than one field

1const options: EvaluateOptions = {
2  // Let's assume you use "remark-flexible-toc" plugin which composes
3  // the table of content (TOC) within the 'vfile.data.toc'
4  vfileDataIntoScope: "toc"; // or fileDataIntoScope: ["toc"];
5};

Now, vfile.data.toc is copied into the scope as scope["toc"], and will be supplied to the MDX via scope.

1# My article
2
3<TableOfContentComponent toc={toc} />

If you need to change the name of the field, specify it for example { name: "toc", as: "headings" }.

1const options: EvaluateOptions = {
2  vfileDataIntoScope: { name: "toc", as: "headings" };
3};

1# My article
2
3<TableOfContentComponent headings={headings} />

If you need to pass all the fields from vfile.data, specify it as true

1const options: EvaluateOptions = {
2  vfileDataIntoScope: true;
3};

The MDXRemote component

Go to the evaluate function

The MDXRemote component is used for rendering the MDX content on the server side. It is a react server component.

1async function MDXRemote(props: MDXRemoteProps): Promise<JSX.Element> {}

The MDXRemote component takes MDXRemoteProps and returns JSX.Element as a promise.

Props of the MDXRemote component

1type MDXRemoteProps<TScope> = {
2  source: Compatible;
3  options?: MDXRemoteOptions<TScope>;
4  components?: MDXComponents;
5  onError?: React.ComponentType<{ error: Error }>
6};

The MDXRemote has internal error handling mechanism as much as it can, in order to do so, it takes onError prop in addition to evaluate function.

[!CAUTION] The eval of the compiled source returns a module MDXModule, and does not throw errors except syntax errors. Some errors throw during the render process which needs you to use an ErrorBoundary.

1import { Suspense } from "react";
2import { MDXRemote, type MDXRemoteOptions } from "next-mdx-remote-client/rsc";
3
4import { ErrorComponent, LoadingComponent } from "../components";
5import { components } from "../mdxComponents";
6
7export default async function MDXComponent({ source }: {source?: string}) {
8  if (!source) {
9    return <ErrorComponent error="The source could not found !" />;
10  }
11
12  const options: MDXRemoteOptions = {
13    /* */
14  };
15
16  return (
17    <Suspense fallback={<LoadingComponent />}>
18      <MDXRemote
19        source={source}
20        options={options}
21        components={components}
22        onError={ErrorComponent}
23      />
24    </Suspense>
25  );
26};

The MDXRemote options (MDXRemoteOptions)

All options are optional.

1type MDXRemoteOptions<TScope> = {
2  mdxOptions?: EvaluateMdxOptions;
3  disableExports?: boolean;
4  disableImports?: boolean;
5  parseFrontmatter?: boolean;
6  scope?: TScope;
7  vfileDataIntoScope?: VfileDataIntoScope;
8};

The details are the same with the EvaluateOptions.

The part associated with Next.js pages router

Go to the part associated with Next.js app router

The next-mdx-remote-client exposes serialize, hydrate functions and MDXClient component for "pages" router.

The serialize function is used on the server side in "pages" router, while as the hydrate and the MDXClient are used on the client side in "pages" router. That is why the "serialize" function is purposefully isolated considering it is intended to run on the server side.

Let's give some examples how to use next-mdx-remote-client in "pages" router first, then explain the exposed functions and component.

Examples for pages router

See a demo application with pages router, visit source code or living web site

An example with javascript

1import { serialize } from 'next-mdx-remote-client/serialize';
2import { MDXClient } from 'next-mdx-remote-client';
3
4import ErrorComponent from '../components/ErrorComponent';
5import Test from '../mdxComponents/Test';
6
7const components = { 
8  Test,
9  wrapper: ({children}) => <div className="mdx-wrapper">{children}</div>,
10}
11
12export default function Page({ mdxSource }) {
13  if ("error" in mdxSource) {
14    return <ErrorComponent error={mdxSource.error} />;
15  }
16
17  return <MDXClient {...mdxSource} components={components} />;
18}
19
20export async function getStaticProps() {
21  const source = "Some **bold text** in MDX, with a component <Test />";
22
23  const mdxSource = await serialize({source});
24
25  return { props: { mdxSource } };
26}

An example with typescript, parsing frontmatter and providing custom data with scope

1import { MDXClient, type MDXComponents } from 'next-mdx-remote-client';
2import { serialize } from "next-mdx-remote-client/serialize";
3import type { SerializeOptions, SerializeResult } from "next-mdx-remote-client/serialize";
4
5import { calculateSomeHow, getSourceSomeHow } from "../utils";
6import ErrorComponent from '../components/ErrorComponent';
7import Test from '../mdxComponents/Test';
8
9type Scope = {
10  readingTime: string;
11};
12
13type Frontmatter = {
14  title: string;
15  author: string;
16};
17
18const components: MDXComponents = { 
19  Test,
20  wrapper: function ({ children }: React.ComponentPropsWithoutRef<"div">) {
21    return <div className="mdx-wrapper">{children}</div>;
22  },
23}
24
25type Props = {
26  mdxSource?: SerializeResult<Frontmatter, Scope>;
27}
28
29export default function Page({ mdxSource }: Props) {
30  if (!mdxSource) {
31    return <ErrorComponent error="The source could not found !" />;
32  }
33
34  if ("error" in mdxSource) {
35    return <ErrorComponent error={mdxSource.error} />;
36  }
37
38  return (
39    <>
40      <h1>{mdxSource.frontmatter.title}</h1>
41      <p>Written by {mdxSource.frontmatter.author}; read in {mdxSource.scope.readingTime}</p>
42      <MDXClient {...mdxSource} components={components} />
43    </>
44  );
45}
46
47export async function getStaticProps() {
48  const source = await getSourceSomeHow();
49
50  if (!source) return { props: {} };
51
52  const options: SerializeOptions<Scope> = {
53    disableImports: true,
54    mdxOptions: {
55      // ...
56    },
57    parseFrontmatter: true,
58    scope: {
59      readingTime: calculateSomeHow(source),
60    },
61  };
62
63  const mdxSource = await serialize<Frontmatter, Scope>({source, options});
64
65  return { props: { mdxSource } };
66}

An example with creating a table of contents (TOC)

I assume you have a MDX file having <TableOfContentComponent /> inside; and you provide some MDX components which have an entry for TableOfContentComponent: (props) => { ... }.

1---
2title: My Article
3---
4# {frontmatter.title}
5
6<TableOfContentComponent toc={toc} />
7
8rest of the article...

You can have a look at an example TOC component in the demo application.

In order to create a table of contents (TOC) I use remark-flexible-toc in the remark plugin list and pass the table of contents objects vFile.data.toc into the scope via the option vfileDataIntoScope. That's it ! So easy !

1import { MDXClient, type MDXComponents } from 'next-mdx-remote-client';
2import { serialize } from "next-mdx-remote-client/serialize";
3import type { SerializeOptions, SerializeResult } from "next-mdx-remote-client/serialize";
4import remarkFlexibleToc, {type TocItem} from "remark-flexible-toc"; // <---------
5
6import { calculateSomeHow, getSourceSomeHow } from "../utils";
7import { ErrorComponent, TableOfContentComponent } from '../components';
8import { Test } from '../mdxComponents';
9
10type Scope = {
11  readingTime: string;
12};
13
14type Frontmatter = {
15  title: string;
16  author: string;
17};
18
19const components: MDXComponents = { 
20  Test,
21  wrapper: function ({ children }: React.ComponentPropsWithoutRef<"div">) {
22    return <div className="mdx-wrapper">{children}</div>;
23  },
24}
25
26type Props = {
27  mdxSource?: SerializeResult<Frontmatter, Scope & {toc: TocItem[]}>;
28}
29
30export default function Page({ mdxSource }: Props) {
31  if (!mdxSource) {
32    return <ErrorComponent error="The source could not found !" />;
33  }
34
35  if ("error" in mdxSource) {
36    return <ErrorComponent error={mdxSource.error} />;
37  }
38
39  return (
40    <>
41      <h1>{mdxSource.frontmatter.title}</h1>
42      <p>Written by {mdxSource.frontmatter.author}; read in {mdxSource.scope.readingTime}</p>
43      <TableOfContentComponent toc={mdxSource.scope.toc /* <----- here added TOC */} />
44      <MDXClient {...mdxSource} components={components} />
45    </>
46  );
47}
48
49export async function getStaticProps() {
50  const source = await getSourceSomeHow();
51
52  if (!source) return { props: {} };
53
54  const options: SerializeOptions<Scope> = {
55    disableImports: true,
56    mdxOptions: {
57      remarkPlugins: [
58        // ...
59        remarkFlexibleToc, // <---------
60      ], 
61    },
62    parseFrontmatter: true,
63    scope: {
64      readingTime: calculateSomeHow(source),
65    },
66    vfileDataIntoScope: "toc", // <---------
67  };
68
69  const mdxSource = await serialize<Frontmatter, Scope>({source, options});
70
71  return { props: { mdxSource } };
72}

Actually, you may not need to access the "frontmatter" and "scope" in JSX, you can use them within MDX directly, and return just <MDXClient /> only.

1// ...
2const components: MDXComponents = { 
3  TableOfContentComponent, // <---------
4  wrapper: function ({ children }: React.ComponentPropsWithoutRef<"div">) {
5    return <div className="mdx-wrapper">{children}</div>;
6  },
7}
8// ...
9export default function Page({ mdxSource }: Props) {
10  // ...
11  return (
12    <MDXClient {...mdxSource} components={components} />
13  );
14}

article.mdx

1# {frontmatter.title}
2
3Written by {frontmatter.author}; read in {readingTime}
4
5<TableOfContentComponent toc={toc} />
6
7rest of the article...

After the examples given, let's dive into the exposed functions and component by next-mdx-remote-client for "pages" router.

The serialize function

Go to the hydrate function or the MDXClient component

1import { serialize } from "next-mdx-remote-client/serialize";

The serialize function is used for compiling the MDX source, in other words, producing the compiled source from MDX source, intended to run on server side at build time.

[!WARNING] The serialize function is asyncronous and to be used within the getStaticProps or the getServerSideProps on the server side. (Off the record, it can be used within an useEffect as well, but this is not recommended because it is a heavy function as having more dependencies).

1async function serialize(props: SerializeProps): Promise<SerializeResult> {}

The serialize function takes SerializeProps and returns SerializeResult as a promise.

Props of the serialize function

1type SerializeProps<TScope> = {
2  source: Compatible;
3  options?: SerializeOptions<TScope>;
4};

Result of the serialize function

Either the compiledSource or the error exists, in addition to frontmatter and scope.

1type SerializeResult<TFrontmatter, TScope> = 
2({ compiledSource: string } | { error: Error })
3& {
4  frontmatter: TFrontmatter;
5  scope: TScope;
6};

The serialize function has internal error handling mechanism for the MDX syntax errors. The catched error is serialized via serialize-error package and attached into the serialize results, further you can deserialize the error on the client, if necessary. You don't need to implement error handling by yourself.

1import { serialize, type SerializeOptions } from "next-mdx-remote-client/serialize";
2import type { Frontmatter, Scope } from "./types"
3
4export async function getStaticProps() {
5  const source = await getSourceSomeHow();
6
7  if (!source) {
8    return { props: {} };
9  }
10
11  const options: SerializeOptions = {
12    /* */
13  };
14
15  const mdxSource = await serialize<Frontmatter, Scope>({
16    source,
17    options,
18  });
19
20  return {
21    props: {
22      mdxSource,
23    },
24  };
25}

If you provide the generic type parameters like await serialize<Frontmatter, Scope>(){}, the frontmatter and the scope get the types, otherwise Record<string, unknown> by default for both.

[!WARNING] Pay attention to the order of the generic type parameters.

The type parameters Frontmatter and Scope should extend Record<string, unknown>. You should use type instead of interface for type parameters otherwise, you will receive an error saying Type 'Xxxx' does not satisfy the constraint 'Record<string, unknown>'. See this issue for more explanation.

The nextjs will send the mdxSource ((compiledSource or error) + frontmatter + scope) to client side.

On client side, you need first to narrow the mdxSource by checking if ("error" in mdxSource) {}.

1type Props = {
2  mdxSource?: SerializeResult<Frontmatter, Scope>;
3}
4
5export default function Page({ mdxSource }: Props) {
6  // ...
7
8  if ("error" in mdxSource) {
9    return <ErrorComponent error={mdxSource.error} />;
10  }
11
12  // ...
13};

The serialize options (SerializeOptions)

All options are optional.

1type SerializeOptions<TScope> = {
2  mdxOptions?: SerializeMdxOptions;
3  disableExports?: boolean;
4  disableImports?: boolean;
5  parseFrontmatter?: boolean;
6  scope?: TScope;
7  vfileDataIntoScope?: VfileDataIntoScope;
8};

Except the mdxOptions, the details are the same with the EvaluateOptions.

mdxOptions

It is a SerializeMdxOptions option to be passed to the @mdx-js/mdx compiler.

1import { type CompileOptions as OriginalCompileOptions } from "@mdx-js/mdx";
2
3type SerializeMdxOptions = Omit<
4  OriginalCompileOptions,
5  "outputFormat" | "providerImportSource"
6>;

As you see, some of the options are omitted and opinionated within the package. For example the outputFormat is always function-body by default. Visit https://mdxjs.com/packages/mdx/#compileoptions for available mdxOptions.

1const options: SerializeOptions = {
2  // ...
3  mdxOptions: {
4    format: "mdx",
5    baseUrl: import.meta.url,
6    development: true,
7    remarkPlugins: [/* */],
8    rehypePlugins: [/* */],
9    recmaPlugins: [/* */],
10    remarkRehypeOptions: {handlers: {/* */}},
11    // ...
12  };
13};

[!WARNING] Here I need to mention about the scope option again for the serialize.

scope

Actually, the serialize doesn't do so much with the scope except you provide the option vfileDataIntoScope for passing data from vfile.data into the scope. Since the scope is passed from the server to the client by nextjs, the scope must be serializable. The scope can not hold function, component , Date, undefined, Error object etc.

If the scope has to have unserializable information or if you don't need or don't want to pass the scope into the serialize, you can pass it into hydrate or MDXClient directly on the client side.

The hydrate function

Go to the serialize function or the MDXClient component

1import { hydrate } from "next-mdx-remote-client/csr";

The hydrate function is used for constructing the compiled source, getting exported information from MDX and returning MDX content to be rendered on the client side.

1function hydrate(props: HydrateProps): HydrateResult {}

The hydrate function takes HydrateProps and returns HydrateResult. The hydrate has no "options" parameter.

Props of the hydrate function

1type HydrateProps = {
2  compiledSource: string;
3  frontmatter?: Record<string, unknown>;
4  scope?: Record<string, unknown>;
5  components?: MDXComponents;
6  disableParentContext?: boolean;
7};

The option disableParentContext is a feature of @mdx-js/mdx. If it is false, the mdx components provided by parent MDXProviders are going to be disregarded.

Result of the hydrate function

1type HydrateResult = {
2  content: JSX.Element;
3  mod: Record<string, unknown>;
4  error?: Error;
5};

The mod object is for exported information from MDX source.

[!TIP] If you need to get the exports from MDX --> use hydrate
If you don't need --> use MDXClient

The hydrate has internal error handling mechanism as much as it can, in order to do so, it returns an error object if it is catched.

[!CAUTION] The eval of the compiled source returns a module MDXModule, and does not throw errors except syntax errors. Some errors throw during the render process which needs you to use an ErrorBoundary.

1import { hydrate, type SerializeResult } from "next-mdx-remote-client/csr";
2
3import { ErrorComponent, TableOfContentComponent } from "../components";
4import { components } from "../mdxComponents";
5import type { Frontmatter, Scope } from "../types"
6
7type Props = {
8  mdxSource?: SerializeResult<Frontmatter, Scope>;
9}
10
11export default function Page({ mdxSource }: Props) {
12  if (!mdxSource) {
13    return <ErrorComponent error="The source could not found !" />;
14  }
15
16  if ("error" in mdxSource) {
17    return <ErrorComponent error={mdxSource.error} />;
18  }
19
20  // Now, mdxSource has {compiledSource, frontmatter, scope}
21
22  const { content, mod, error } = hydrate({ ...mdxSource, components });
23
24  if (error) {
25    return <ErrorComponent error={error} />;
26  }
27
28  // You can use the "mod" object for exported information from the MDX as you wish
29
30  return (
31    <>
32      <h1>{mdxSource.frontmatter.title}</h1>
33      <div><em>{mod.something}</em></div>
34      <TableOfContentComponent toc={mdxSource.scope.toc} />
35      {content}
36    </>
37  );
38};

In the above example, I assume you use remark-flexible-toc remark plugin in order to collect the headings from the MDX content, and you pass that information into the scope via vfileDataIntoScope option within the serialize on the server side.

The MDXClient component

Go to the serialize function or the hydrate function

1import { MDXClient } from "next-mdx-remote-client/csr";

The MDXClient component is used for rendering the MDX content on the client side.

1function MDXClient(props: MDXClientProps): JSX.Element {}

The MDXClient component takes MDXClientProps and returns JSX.Element. The MDXClient has no "options" parameter like hydrate.

Props of the MDXClient component

1type MDXClientProps = {
2  compiledSource: string;
3  frontmatter?: Record<string, unknown>;
4  scope?: Record<string, unknown>;
5  components?: MDXComponents;
6  disableParentContext?: boolean;
7  onError?: React.ComponentType<{ error: Error }>
8};

The option disableParentContext is a feature of @mdx-js/mdx. If it is false, the mdx components provided by parent MDXProviders are going to be disregarded.

[!TIP] If you need to get the exports from MDX --> use hydrate
If you don't need --> use MDXClient

The MDXClient has internal error handling mechanism as much as it can, in order to do so, it takes onError prop in addition to hydrate function.

[!CAUTION] The eval of the compiled source returns a module MDXModule, and does not throw errors except syntax errors. Some errors throw during the render process which needs you to use an ErrorBoundary.

1import { MDXClient, type SerializeResult } from "next-mdx-remote-client/csr";
2
3import { ErrorComponent, TableOfContentComponent } from "../components";
4import { components } from "../mdxComponents";
5import type { Frontmatter, Scope } from "../types"
6
7type Props = {
8  mdxSource?: SerializeResult<Frontmatter, Scope>;
9}
10
11export default function Page({ mdxSource }: Props) {
12  if (!mdxSource) {
13    return <ErrorComponent error="The source could not found !" />;
14  }
15
16  if ("error" in mdxSource) {
17    return <ErrorComponent error={mdxSource.error} />;
18  }
19
20  // Now, mdxSource has {compiledSource, frontmatter, scope}
21
22  return (
23    <>
24      <h1>{mdxSource.frontmatter.title}</h1>
25      <TableOfContentComponent toc={mdxSource.scope.toc} />
26      <MDXClient
27        {...mdxSource}
28        components={components}
29        onError={ErrorComponent}
30      />
31    </>
32  );
33};

In the above example, I assume you use remark-flexible-toc remark plugin in order to collect the headings from the MDX content, and you pass that information into the scope via vfileDataIntoScope option within the serialize on the server side.

The hydrateLazy function and the MDXClientLazy component

The next-mdx-remote-client exports additional versions, say, the hydrateLazy and the MDXClientLazy, which both have the same functionality, props, results with the hydrate and the MDXClient, correspondently.

The only difference is the hydration process takes place lazily on the browser within a window.requestIdleCallback in a useEffect. You can use hydrateLazy or MDXClientLazy in order to defer hydration of the content and immediately serve the static markup.

1import { hydrateLazy, MDXClientLazy } from "next-mdx-remote-client/csr";

When you use hydrateLazy, and want to get the exports from MDX via mod object, please be aware that the mod object is always empty {} at first render, then it will get actual exports at second render.

[!NOTE] Lazy hydration defers hydration of the components on the client. This is an optimization technique to improve the initial load of the application, but may introduce unexpected delays in interactivity for any dynamic content within the MDX content.

This will add an additional wrapping div around the rendered MDX, which is necessary to avoid hydration mismatches during render.

For further explanation about the lazy hydration see next-mdx-remote notes.

The hydrateAsync function and the MDXClientAsync component

The next-mdx-remote-client exports additional versions, say, the hydrateAsync and the MDXClientAsync.

These have additional props and options, but here, I don't want to give the details since I created them for experimental to show the import statements on the client side don't work. You can have a look at the github repository for the code and the tests.

The main difference is that the eval of the compiled source takes place in a useEffect on the browser, since the compile source has await keyword for import statements.

1import { hydrateAsync, MDXClientAsync } from "next-mdx-remote-client/csr";

[!NOTE]
I believe, it is viable somehow using dynamic API if the vercel supports for a solution for the pages router via import.meta APIs. During the compilation of the MDX in the serialize, a remark/recma plugin can register the imported modules into the import.meta.url via a nextjs API (needs support of vercel) for them will be available to download/import on the client side via dynamic api. This is my imagination.

The MDXProvider component

The package exports the MDXProvider from @mdx-js/react, in order the developers don't need to install the @mdx-js/react.

1import { MDXProvider } from "next-mdx-remote-client/csr";

The <MDXProvider /> makes the mdx components available to any <MDXClient /> or hydrate's { content } being rendered in the application, as a child status of that provider.

For example, you can wrap the whole application so as you do not need to supply the mdx components into any <MDXClient /> or hydrate's { content }.

1import { MDXProvider } from 'next-mdx-remote-client';
2
3import { components } from "../mdxComponents"; 
4
5export default function App({ Component, pageProps }) {
6  return (
7    <MDXProvider components={components}>
8      <Component {...pageProps} />
9    </MDXProvider>
10  )
11}

[!NOTE] How this happens, because the next-mdx-remote-client injects the useMdxComponents context hook from @mdx-js/react during the function construction of the compiled source, internally. Pay attention that it is valid for only MDXClient and hydrate functions.

[!CAUTION] Since MDXRemote as a react server component can not read the context, MDXProvider is effectless when used within the nextjs app router for MDXRemote, which is also for evaluate.

MDX Components

You can provide a map of custom MDX components, which is a feature of @mdx-js/mdx, in order to replace HTML tags (see the list of markdown syntax and equivalent HTML tags) with the custom components.

Typescript users can use MDXComponents from mdx/types, which is exported by this package as well.

../mdxComponents/index.ts

1import { type MDXComponents } from "next-mdx-remote-client";
2
3import dynamic from "next/dynamic";
4import Image from "next/image";
5import Link from "next/link";
6
7import { Typography } from "@material-ui/core";
8import { motion } from 'framer-motion'
9
10import Hello from "./Hello";
11import CountButton from "./CountButton";
12import BlockQuote, { default as blockquote } from "./BlockQuote";
13import pre from "./pre";
14
15export const mdxComponents: MDXComponents = {
16  Hello,
17  CountButton,
18  Dynamic: dynamic(() => import("./dynamic")),
19  Image,
20  Link,
21  motion: { div: () => <div>Hello world</div> },
22  h2: (props: React.ComponentPropsWithoutRef<"h2">) => (
23    <Typography variant="h2" {...props} />
24  ),
25  strong: (props: React.ComponentPropsWithoutRef<"strong">) => (
26    <strong className="custom-strong" {...props} />
27  ),
28  em: (props: React.ComponentPropsWithoutRef<"em">) => (
29    <em className="custom-em" {...props} />
30  ),
31  pre,
32  blockquote,
33  BlockQuote,
34  wrapper: (props: { children: any }) => {
35    return <div id="mdx-layout">{props.children}</div>;
36  }
37};

[!NOTE] The wrapper is a special key, if you want to wrap the MDX content with a HTML container element.

./data/my-article.mdx

1---
2title: "My Article"
3author: "ipikuka"
4---
5_Read in {readingTime}, written by <Link href="#">**{frontmatter.author}**</Link>_
6
7# {frontmatter.title}
8
9## Sub heading for custom components
10
11<Hello name={foo} />
12
13<CountButton />
14
15<Dynamic />
16
17<Image src="/images/cover.png" alt="cover" width={180} height={40} />
18
19<BlockQuote>
20  I am blackquote content
21</BlockQuote>
22
23<motion.div animate={{ x: 100 }} />
24
25## Sub heading for some markdown elements
26
27![cover](/images/cover.png)
28
29Here is _italic text_ and **strong text**
30
31> I am blackquote content

Utility getFrontmatter

The package exports one utility getFrontmatter which is for getting frontmatter without compiling the source. You can get the fronmatter and the stripped source by using the getFrontmatter which employs the same frontmatter extractor vfile-matter used within the package.

1import { getFrontmatter } from "next-mdx-remote-client/utils";
2
3const { frontmatter, strippedSource } = getFrontmatter<TFrontmatter>(source);

If you provide the generic type parameter, it ensures the frontmatter gets the type, otherwise Record<string, unknown> by default.

If there is no frontmatter in the source, the frontmatter will be empty object {}.

[!IMPORTANT]
If you use next-mdx-remote and want to get frontmatter without compiling the source !
The subpath next-mdx-remote-client/utils is isolated from other features of the package and it does cost minimum. So, anyone can use next-mdx-remote-client/utils while using next-mdx-remote.

Types

The next-mdx-remote-client is fully typed with TypeScript.

The package exports the types for server side (rsc):

• EvaluateProps
• EvaluateOptions
• EvaluateResult
• MDXRemoteProps
• MDXRemoteOptions

The package exports the types for client side (csr):

• HydrateProps
• HydrateResult
• MDXClientProps
• SerializeResult

The package exports the types for the serialize function:

• SerializeProps
• SerializeOptions
• SerializeResult

In addition, the package exports the types from mdx/types so that developers do not need to import mdx/types:

• MDXComponents
• MDXContent
• MDXProps
• MDXModule

Compatibility

The next-mdx-remote-client works with unified version 6+ ecosystem since it is compatible with MDX version 3.

Security

Allowance of the export declarations and the import declarations in MDX source, if you don't have exact control on the content, may cause vulnerabilities and harmful activities. The next-mdx-remote-client gives options for disabling them.

But, you need to use a custom recma plugin for disabiling the import expressions like await import("xyz") since the next-mdx-remote-client doesn't touch the import expressions.

Eval a string of JavaScript can be a dangerous and may cause enabling XSS attacks, which is how the next-mdx-remote-client APIs do. Please, take your own measures while passing the user input.

If there is a Content Security Policy (CSP) on the website that disallows code evaluation via eval or new Function(), it is needed to loosen that restriction in order to utilize next-mdx-remote-client, which can be done using unsafe-eval.

Some Plugins

I like to contribute the Unified / Remark / MDX ecosystem, so I recommend you to have a look my plugins.

My Remark Plugins

• remark-flexible-code-titles – Remark plugin to add titles or/and containers for the code blocks with customizable properties
• remark-flexible-containers – Remark plugin to add custom containers with customizable properties in markdown
• remark-ins – Remark plugin to add ins element in markdown
• remark-flexible-paragraphs – Remark plugin to add custom paragraphs with customizable properties in markdown
• remark-flexible-markers – Remark plugin to add custom mark element with customizable properties in markdown
• remark-flexible-toc – Remark plugin to expose the table of contents via Vfile.data or via an option reference
• remark-mdx-remove-esm – Remark plugin to remove import and/or export statements (mdxjsEsm)

My Rehype Plugins

• rehype-pre-language – Rehype plugin to add language information as a property to pre element

My Recma Plugins

• recma-mdx-escape-missing-components – Recma plugin to set the default value () => null for the Components in MDX in case of missing or not provided so as not to throw an error
• recma-mdx-change-props – Recma plugin to change the props parameter into the _props in the function _createMdxContent(props) {/* */} in the compiled source in order to be able to use {props.foo} like expressions. It is useful for the next-mdx-remote or next-mdx-remote-client users in nextjs applications.

License

MPL 2.0 License © ipikuka

Keywords

🟩 @mdx-js 🟩 next/mdx 🟩 next-mdx-remote 🟩 next-mdx-remote-client