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[File & Storage](/categories/file-storage) 4. / 5. avoidwork/filesize.js ActiveLibrary[File & Storage](/categories/file-storage) avoidwork/filesize.js ===================== JavaScript library to generate a human readable String describing the file size 6.2.1(5y ago)1.7k38698BSD-3-ClauseJavaScriptCI passing Since Jan 4Pushed 2w ago14 watchersCompare [ Source](https://github.com/avoidwork/filesize.js)[ Packagist](https://packagist.org/packages/avoidwork/filesize.js)[ Docs](http://filesizejs.com)[ GitHub Sponsors](https://github.com/avoidwork)[ RSS](/packages/avoidwork-filesizejs/feed)WikiDiscussions master Synced today READMEChangelogDependenciesVersions (46)Used By (0) filesize ======== [](#filesize) [![npm version](https://camo.githubusercontent.com/cd91e9e58f9ac52c99873a100e4112c5ed06f05fc55ffbaa82578865fed33188/68747470733a2f2f62616467652e667572792e696f2f6a732f66696c6573697a652e737667)](https://www.npmjs.com/package/filesize)[![Node.js Version](https://camo.githubusercontent.com/1a716e5ec9b40770f43ca70e9b63b13104c7fbbb45379ceb854ae2d96a908ad1/68747470733a2f2f696d672e736869656c64732e696f2f6e6f64652f762f66696c6573697a652e737667)](https://nodejs.org/)[![License](https://camo.githubusercontent.com/b3775a2de17853a90995faa104f941eef3ad3c40cc89e34b8b1eaea014614d4e/68747470733a2f2f696d672e736869656c64732e696f2f62616467652f4c6963656e73652d425344253230332d2d436c617573652d626c75652e737667)](https://opensource.org/licenses/BSD-3-Clause)[![Build Status](https://github.com/avoidwork/filesize.js/actions/workflows/ci.yml/badge.svg)](https://github.com/avoidwork/filesize.js/actions) A lightweight, high-performance file size utility that converts bytes to human-readable strings. Zero dependencies. 100% test coverage. Why filesize? ------------- [](#why-filesize) - **Zero dependencies** - Pure JavaScript, no external packages - **100% test coverage** - Reliable, well-tested codebase - **TypeScript ready** - Full type definitions included - **Multiple standards** - SI, IEC, and JEDEC support - **Localization** - Intl API for international formatting - **BigInt support** - Handle extremely large file sizes - **Functional API** - Partial application for reusable formatters - **Browser & Node.js** - Works everywhere Installation ------------ [](#installation) ``` npm install filesize ``` TypeScript ---------- [](#typescript) Fully typed with TypeScript definitions included: ``` import { filesize, partial } from 'filesize'; const result: string = filesize(1024); const formatted: { value: number; symbol: string; exponent: number; unit: string } = filesize(1024, { output: 'object' }); const formatter: (arg: number | bigint) => string = partial({ standard: 'iec' }); ``` Usage ----- [](#usage) ``` import {filesize, partial} from "filesize"; filesize(1024); // "1.02 kB" filesize(265318); // "265.32 kB" filesize(1024, {standard: "iec"}); // "1 KiB" filesize(1024, {bits: true}); // "8.19 kbit" ``` ### Partial Application [](#partial-application) ``` import {partial} from "filesize"; const formatBinary = partial({standard: "iec"}); formatBinary(1024); // "1 KiB" formatBinary(1048576); // "1 MiB" ``` Options ------- [](#options) OptionTypeDefaultDescription`bits`boolean`false`Calculate bits instead of bytes`base`number`-1`Number base (2 for binary, 10 for decimal, -1 for auto)`round`number`2`Decimal places to round`locale`string|boolean`""`Locale for formatting, `true` for system locale`localeOptions`Object`{}`Additional locale options`separator`string`""`Custom decimal separator`spacer`string`" "`Value-unit separator`symbols`Object`{}`Custom unit symbols`standard`string`""`Unit standard (`si`, `iec`, `jedec`)`output`string`"string"`Output format (`string`, `array`, `object`, `exponent`)`fullform`boolean`false`Use full unit names`fullforms`Array`[]`Custom full unit names`exponent`number`-1`Force specific exponent (-1 for auto)`roundingMethod`string`"round"`Math method (`round`, `floor`, `ceil`)`precision`number`0`Significant digits (0 for auto)`pad`boolean`false`Pad decimal placesOutput Formats -------------- [](#output-formats) ``` // String (default) filesize(1536); // "1.54 kB" // Array filesize(1536, {output: "array"}); // [1.54, "kB"] // Object filesize(1536, {output: "object"}); // {value: 1.54, symbol: "kB", exponent: 1, unit: "kB"} // Exponent filesize(1536, {output: "exponent"}); // 1 ``` Standards --------- [](#standards) ``` // SI (default, base 10) filesize(1000); // "1 kB" // IEC (binary, requires base: 2) filesize(1024, {base: 2, standard: "iec"}); // "1 KiB" // JEDEC (binary calculation, traditional symbols) filesize(1024, {standard: "jedec"}); // "1 KB" ``` Examples -------- [](#examples) ``` // Bits filesize(1024, {bits: true}); // "8.19 kbit" filesize(1024, {bits: true, base: 2}); // "8 Kibit" // Full form filesize(1024, {fullform: true}); // "1.02 kilobytes" filesize(1024, {base: 2, fullform: true}); // "1 kibibyte" // Custom separator filesize(265318, {separator: ","}); // "265,32 kB" // Padding filesize(1536, {round: 3, pad: true}); // "1.536 kB" // Precision filesize(1536, {precision: 3}); // "1.54 kB" // Locale filesize(265318, {locale: "de"}); // "265,32 kB" // Custom symbols filesize(1, {symbols: {B: "Б"}}); // "1 Б" // BigInt support filesize(BigInt(1024)); // "1.02 kB" // Negative numbers filesize(-1024); // "-1.02 kB" ``` Error Handling -------------- [](#error-handling) ``` try { filesize("invalid"); } catch (error) { // TypeError: "Invalid number" } try { filesize(1024, {roundingMethod: "invalid"}); } catch (error) { // TypeError: "Invalid rounding method" } ``` Testing ------- [](#testing) ``` npm test # Run all tests (lint + node:test) npm run test:watch # Live test watching ``` **100% test coverage** with 149 tests: ``` --------------|---------|----------|---------|---------|------------------- File | % Stmts | % Branch | % Funcs | % Lines | Uncovered Line #s --------------|---------|----------|---------|---------|------------------- All files | 100 | 100 | 100 | 100 | constants.js | 100 | 100 | 100 | 100 | filesize.js | 100 | 100 | 100 | 100 | helpers.js | 100 | 100 | 100 | 100 | --------------|---------|----------|---------|---------|------------------- ``` Development ----------- [](#development) ``` npm install # Install dependencies npm run dev # Development mode with live reload npm run build # Build distributions npm run lint # Check code style npm run lint:fix # Auto-fix linting issues ``` ### Project Structure [](#project-structure) ``` filesize.js/ ├── src/ │ ├── filesize.js # Main implementation (285 lines) │ ├── helpers.js # Helper functions (215 lines) │ └── constants.js # Constants (81 lines) ├── tests/ │ └── unit/ ├── dist/ # Built distributions └── types/ # TypeScript definitions ``` Performance ----------- [](#performance) - **Basic conversions**: ~16-27M ops/sec - **With options**: ~5-13M ops/sec - **Locale formatting**: ~91K ops/sec (use sparingly) **Optimization tips:** 1. Cache `partial()` formatters for reuse 2. Avoid locale formatting in performance-critical code 3. Use `object` output for fastest structured data access Contributing ------------ [](#contributing) We welcome contributions! Please see our [Contributing Guidelines](https://github.com/avoidwork/filesize.js/blob/master/CONTRIBUTING.md) for details. Changelog --------- [](#changelog) See [CHANGELOG.md](https://github.com/avoidwork/filesize.js/blob/master/CHANGELOG.md) for a history of changes. License ------- [](#license) Copyright (c) 2026 Jason Mulligan Licensed under the BSD-3 license. ### Health Score 55 — FairBetter than 97% of packages Maintenance63 Regular maintenance activity Popularity40 Moderate usage in the ecosystem Community31 Small or concentrated contributor base Maturity76 Established project with proven stability Bus Factor1 Top contributor holds 78.5% of commits — single point of failure How is this calculated?**Maintenance (25%)** — Last commit recency, latest release date, and issue-to-star ratio. Uses a 2-year decay window. **Popularity (30%)** — Total and monthly downloads, GitHub stars, and forks. Logarithmic scaling prevents top-heavy scores. **Community (15%)** — Contributors, dependents, forks, watchers, and maintainers. Measures real ecosystem engagement. **Maturity (30%)** — Project age, version count, PHP version support, and release stability. ### Release Activity Cadence Every ~51 days Recently: every ~132 days Total 46 Last Release 1907d ago Major Versions 3.6.1 → 4.0.02019-01-12 4.2.1 → 5.0.02019-10-01 5.0.3 → 6.0.02019-10-31 ### Community Maintainers ![](https://www.gravatar.com/avatar/c57b31c04075b96bd716ae6b0c43f874d8c67c088d0adf722ddec6feefa76508?d=identicon)[avoidwork](/maintainers/avoidwork) --- Top Contributors [![avoidwork](https://avatars.githubusercontent.com/u/369698?v=4)](https://github.com/avoidwork "avoidwork (435 commits)")[![dependabot[bot]](https://avatars.githubusercontent.com/in/29110?v=4)](https://github.com/dependabot[bot] "dependabot[bot] (84 commits)")[![realityking](https://avatars.githubusercontent.com/u/628508?v=4)](https://github.com/realityking "realityking (7 commits)")[![christopherscott](https://avatars.githubusercontent.com/u/125866?v=4)](https://github.com/christopherscott "christopherscott (3 commits)")[![tomoto](https://avatars.githubusercontent.com/u/552888?v=4)](https://github.com/tomoto "tomoto (2 commits)")[![getsnoopy](https://avatars.githubusercontent.com/u/2997884?v=4)](https://github.com/getsnoopy "getsnoopy (2 commits)")[![abaltuta](https://avatars.githubusercontent.com/u/37699890?v=4)](https://github.com/abaltuta "abaltuta (2 commits)")[![gitter-badger](https://avatars.githubusercontent.com/u/8518239?v=4)](https://github.com/gitter-badger "gitter-badger (1 commits)")[![gurpreetbaidwan](https://avatars.githubusercontent.com/u/4227224?v=4)](https://github.com/gurpreetbaidwan "gurpreetbaidwan (1 commits)")[![laughinghan](https://avatars.githubusercontent.com/u/225809?v=4)](https://github.com/laughinghan "laughinghan (1 commits)")[![litvinok](https://avatars.githubusercontent.com/u/1155664?v=4)](https://github.com/litvinok "litvinok (1 commits)")[![lngsx](https://avatars.githubusercontent.com/u/1572632?v=4)](https://github.com/lngsx "lngsx (1 commits)")[![pdehaan](https://avatars.githubusercontent.com/u/557895?v=4)](https://github.com/pdehaan "pdehaan (1 commits)")[![rnike](https://avatars.githubusercontent.com/u/48589760?v=4)](https://github.com/rnike "rnike (1 commits)")[![ryanramage](https://avatars.githubusercontent.com/u/795834?v=4)](https://github.com/ryanramage "ryanramage (1 commits)")[![ryanrhee](https://avatars.githubusercontent.com/u/242548?v=4)](https://github.com/ryanrhee "ryanrhee (1 commits)")[![starius](https://avatars.githubusercontent.com/u/920155?v=4)](https://github.com/starius "starius (1 commits)")[![tomoto-hitachi](https://avatars.githubusercontent.com/u/57977241?v=4)](https://github.com/tomoto-hitachi "tomoto-hitachi (1 commits)")[![vitormil](https://avatars.githubusercontent.com/u/391209?v=4)](https://github.com/vitormil "vitormil (1 commits)")[![wangxingkai](https://avatars.githubusercontent.com/u/6101654?v=4)](https://github.com/wangxingkai "wangxingkai (1 commits)") --- Tags bitsbytesfilefilesizefilesystemiecjedecsimplesizesize-calculationfilereadablefile systemsizefilesize ### Embed Badge ![Health badge](/badges/avoidwork-filesizejs/health.svg) ``` [![Health](https://phpackages.com/badges/avoidwork-filesizejs/health.svg)](https://phpackages.com/packages/avoidwork-filesizejs) ``` ### Alternatives [league/flysystem File storage abstraction for PHP 13.6k679.9M2.5k](/packages/league-flysystem)[league/flysystem-aws-s3-v3 AWS S3 filesystem adapter for Flysystem. 1.7k285.7M1.0k](/packages/league-flysystem-aws-s3-v3)[knplabs/gaufrette PHP library that provides a filesystem abstraction layer 2.5k41.5M133](/packages/knplabs-gaufrette)[knplabs/knp-gaufrette-bundle Allows to easily use the Gaufrette library in a Symfony project 72430.0M102](/packages/knplabs-knp-gaufrette-bundle)[league/flysystem-local Local filesystem adapter for Flysystem. 225267.1M89](/packages/league-flysystem-local)[league/flysystem-memory In-memory filesystem adapter for Flysystem. 8737.3M276](/packages/league-flysystem-memory) PHPackages © 2026 [Directory](/)[Categories](/categories)[Trending](/trending)[Changelog](/changelog)[Analyze](/analyze)