pretty-bytes

Convert bytes to a human readable string: 1337 → 1.34 kB

Useful for displaying file sizes for humans.

Note that it uses base-10 (e.g. kilobyte). Read about the difference between kilobyte and kibibyte.

Install

1npm install pretty-bytes

Usage

1import prettyBytes from 'pretty-bytes';
2
3prettyBytes(1337);
4//=> '1.34 kB'
5
6prettyBytes(100);
7//=> '100 B'
8
9// Display with units of bits
10prettyBytes(1337, {bits: true});
11//=> '1.34 kbit'
12
13// Display file size differences
14prettyBytes(42, {signed: true});
15//=> '+42 B'
16
17// Localized output using German locale
18prettyBytes(1337, {locale: 'de'});
19//=> '1,34 kB'

API

prettyBytes(number, options?)

number

Type: number | bigint

The number to format.

options

Type: object

signed

Type: boolean
Default: false

Include plus sign for positive numbers. If the difference is exactly zero a space character will be prepended instead for better alignment.

bits

Type: boolean
Default: false

Format the number as bits instead of bytes. This can be useful when, for example, referring to bit rate.

binary

Type: boolean
Default: false

Format the number using the Binary Prefix instead of the SI Prefix. This can be useful for presenting memory amounts. However, this should not be used for presenting file sizes.

locale

Type: boolean | string
Default: false (No localization)

Important: Only the number and decimal separator are localized. The unit title is not and will not be localized.

• If true: Localize the output using the system/browser locale.
• If string: Expects a BCP 47 language tag (For example: en, de, …)
• If string[]: Expects a list of BCP 47 language tags (For example: en, de, …)

minimumFractionDigits

Type: number
Default: undefined

The minimum number of fraction digits to display.

If neither minimumFractionDigits or maximumFractionDigits are set, the default behavior is to round to 3 significant digits.

1import prettyBytes from 'pretty-bytes';
2
3// Show the number with at least 3 fractional digits
4prettyBytes(1900, {minimumFractionDigits: 3});
5//=> '1.900 kB'
6
7prettyBytes(1900);
8//=> '1.9 kB'

maximumFractionDigits

Type: number
Default: undefined

The maximum number of fraction digits to display.

If neither minimumFractionDigits or maximumFractionDigits are set, the default behavior is to round to 3 significant digits.

1import prettyBytes from 'pretty-bytes';
2
3// Show the number with at most 1 fractional digit
4prettyBytes(1920, {maximumFractionDigits: 1});
5//=> '1.9 kB'
6
7prettyBytes(1920);
8//=> '1.92 kB'

space

Type: boolean
Default: true

Put a space between the number and unit.

1import prettyBytes from 'pretty-bytes';
2
3prettyBytes(1920, {space: false});
4//=> '1.9kB'
5
6prettyBytes(1920);
7//=> '1.92 kB'

FAQ

Why kB and not KB?

k is the standardized SI prefix for kilo.

Related

• pretty-bytes-cli - CLI for this module
• pretty-ms - Convert milliseconds to a human readable string