Get the UTF-8 byte length of a string.

Features

- Fastest available library in JavaScript.
- Works on all platforms (Node.js, browsers, Deno, etc.)

Example

``js
import stringByteLength from 'string-byte-length'

stringByteLength('test') // 4
stringByteLength(' ') // 1
stringByteLength('\0') // 1
stringByteLength('±') // 2
stringByteLength('★') // 3
stringByteLength('🦄') // 4
`

Install

`bash
npm install string-byte-length
`

This package works in both Node.js >=18.18.0 and
browsers.

This is an ES module. It must be loaded using
an import or import() statement,
not require(). If TypeScript is used, it must be configured to
output ES modules,
not CommonJS.

Alternatives

This library uses a mix of multiple algorithms:

- In Node.js: Buffer.byteLength()
- Otherwise:
- On big strings: TextEncoder
- On small strings: String.charCodeAt()

String.length

string.length
retrieves the number of characters (or
"code units").
This is different from computing the number of bytes when the string is
serialized (for example in a file or network request) since UTF-8 characters can
be 1 to 4 bytes long.

Buffer.byteLength()

Buffer.byteLength(string)
is very fast since it uses
V8's C++ implementation.
However, it only works with Node.js.

Buffer.from()

Buffer.from(string).length
has similar pros/cons as Buffer.byteLength but is
slower.

TextEncoder

new TextEncoder().encode(string)
is fast as it relies on lower-level code. However, it is slower on small
strings.

Also, while widely supported, a few platforms
(like Opera mini) might still miss it.

Blob

[new Blob([string]).size](https://developer.mozilla.org/en-US/docs/Web/API/Blob/size)
has similar pros/cons as TextEncoder but is
slower.

String.charCodeAt()

String.charCodeAt()
can be used on each character to compute its UTF-8 byte length based on the
resulting codepoint.

This works on all platforms and is fast on small strings. However, it is slower
than other methods on big strings.

String.codePointAt()

String.codePointAt()
has similar props/cons as String.charCodeAt() but is
slower.

encodeURI()

encodeURI(string)
or
encodeURIComponent(string)
can be used by counting % sequences separately, such as
encodeURI(string).split(/%..|./u).length - 1. However, this method is
very slow.

Benchmarks

`
String length
0 1 1e1 1e2 1e3 1e4 1e5 1e6 1e7 1e8
Only ASCII Buffer.byteLength() 15.39ns 20.12ns 24.9ns 35.4ns 108ns 817ns 9.76μs 85.1μs 833μs 10.1ms
String.charCodeAt() 3.32ns 6.20ns 22.3ns 163.0ns 1440ns 14200ns 143.00μs 1440.0μs 23600μs 236.0ms
String.codePointAt() 2.72ns 5.20ns 33.5ns 252.0ns 2550ns 23800ns 239.00μs 2380.0μs 23000μs 330.0ms
TextEncoder 116.98ns 123.29ns 123.0ns 129.0ns 169ns 475ns 15.60μs 186.0μs 2520μs 32.5ms
Buffer.from() 36.89ns 146.34ns 175.0ns 227.2ns 432ns 3944ns 48.10μs 271.5μs 3191μs 53.0ms
Blob 9003.03ns 9503.59ns 12311.6ns 9821.1ns 13836ns 21288ns 78.77μs 299.3μs 3029μs 74.9ms
encodeURIComponent() 36.60ns 52.06ns 96.8ns 390.2ns 3257ns 33663ns 323.74μs 3427.8μs 34392μs 358.7ms
encodeURI() 35.91ns 78.32ns 341.2ns 2861.3ns 27141ns 278114ns 3538.72μs 34851.7μs 382012μs 3583.3ms

Mostly ASCII Buffer.byteLength() 15.39ns 22.9ns 28.4ns 79.5ns 453ns 4.34μs 42.9μs 426μs 4.54ms 44.6ms
Very few non-ASCII String.charCodeAt() 3.32ns 8.1ns 27.6ns 190.0ns 1680ns 16.50μs 161.0μs 1640μs 26.90ms 267.0ms
String.codePointAt() 2.72ns 6.8ns 34.3ns 258.0ns 3630ns 34.60μs 328.0μs 3390μs 33.10ms 329.0ms
TextEncoder 116.98ns 122.0ns 136.0ns 218.0ns 948ns 8.32μs 93.5μs 920μs 9.71ms 103.0ms
Buffer.from() 36.89ns 149.0ns 186.2ns 326.9ns 1901ns 20.89μs 195.4μs 1907μs 18.24ms 193.3ms
Blob 9003.03ns 10037.0ns 9659.6ns 9747.9ns 11271ns 32.85μs 190.6μs 1798μs 14.48ms 173.5ms
encodeURIComponent() 36.60ns 242.8ns 273.8ns 650.8ns 4351ns 43.17μs 405.3μs 4311μs 43.29ms 467.9ms
encodeURI() 35.91ns 256.0ns 492.2ns 3065.5ns 28590ns 288.46μs 3575.2μs 35704μs 365.33ms 3493.0ms

Mostly ASCII Buffer.byteLength() 15.39ns 22.9ns 28.4ns 101ns 807ns 7.55μs 75.7μs 735μs 7.64ms 77.0ms
Some non-ASCII String.charCodeAt() 3.32ns 8.1ns 25.9ns 208ns 1910ns 18.40μs 183.0μs 1850μs 29.8ms 294.0ms
String.codePointAt() 2.72ns 6.8ns 31.8ns 281ns 2770ns 26.20μs 263.0μs 2620μs 27.0ms 365.0ms
TextEncoder 116.98ns 122.0ns 132.0ns 248ns 1400ns 12.80μs 138.0μs 1370μs 14.40ms 152.0ms
Buffer.from() 36.89ns 149.0ns 186.2ns 391ns 2758ns 33.08μs 309.9μs 2815μs 29.79ms 308.2ms
Blob 9003.03ns 10037.0ns 9659.6ns 12400ns 16406ns 41.63μs 277.1μs 2293μs 22.84ms 267.5ms
encodeURIComponent() 36.60ns 242.8ns 273.8ns 1865ns 17458ns 168.61μs 1886.2μs 24200μs 411ms n/a
encodeURI() 35.91ns 256.0ns 492.2ns 4216ns 41403ns 404.00μs 5227.7μs 52100μs 466ms n/a

Only non-ASCII Buffer.byteLength() 15.39ns 22.9ns 53.5ns 373ns 3.59μs 35.2μs 380μs 3.81ms 35.6ms 351ms
String.charCodeAt() 3.32ns 8.1ns 45.5ns 404ns 3.69μs 38.2μs 361μs 3.69ms 51.1ms 517ms
String.codePointAt() 2.72ns 6.8ns 44.7ns 407ns 3.92μs 38.9μs 389μs 4.18ms 63.9ms 638ms
TextEncoder 116.98ns 122.0ns 168.0ns 597ns 4.62μs 44.5μs 470μs 4.79ms 53.9ms 525ms
Buffer.from() 36.89ns 149.0ns 243.1ns 1047ns 9.91μs 129.3μs 1328μs 12.97ms 123.5ms 1229ms
Blob 9003.03ns 10037.0ns 9639.7ns 15341ns 25.18μs 114.5μs 1005μs 9.61ms 109.4ms 979ms
encodeURIComponent() 36.60ns 242.8ns 1572.9ns 14175ns 132.62μs 1477.7μs 23932μs 448.94ms 3890.0ms n/a
encodeURI() 35.91ns 256.0ns 1451.3ns 14172ns 132.73μs 1619.8μs 18343μs 177.13ms 1670.0ms n/a
`

Related projects

- string-byte-slice: Like
string.slice() but bytewise
- truncate-json: Truncate a JSON
string

Support

For any question, _don't hesitate_ to submit an issue on GitHub.

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Code of conduct in order to promote a positive and
inclusive environment.

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