rembesbuild
esbuild <entrypoint> --outdir=out --bundle
bun
bun build <entrypoint> --outdir=out
In Bun’s CLI, simple boolean flags like `--minify` do not accept an argument. Other flags like `--outdir <path>` do accept an argument; these flags can be written as `--outdir out` or `--outdir=out`. Some flags like `--define` can be specified several times: `--define foo=bar --define bar=baz`.
esbuild
bun build
Notes
`--bundle`
n/a
Bun always bundles, use `--no-bundle` to disable this behavior.
`--define:K=V`
`--define K=V`
Small syntax difference; no colon.
`esbuild --define:foo=bar`
`bun build --define foo=bar`
`--external:<pkg>`
`--external <pkg>`
Small syntax difference; no colon.
`esbuild --external:react`
`bun build --external react`
`--format`
`--format`
Bun supports `"esm"` and `"cjs"` currently, but more module formats are planned. esbuild defaults to `"iife"`.
`--loader:.ext=loader`
`--loader .ext:loader`
Bun supports a different set of built-in loaders than esbuild; see Bundler > Loaders for a complete reference. The esbuild loaders `dataurl`, `binary`, `base64`, `copy`, and `empty` are not yet implemented.
The syntax for `--loader` is slightly different.
`esbuild app.ts --bundle --loader:.svg=text`
`bun build app.ts --loader .svg:text`
`--minify`
`--minify`
No differences
`--outdir`
`--outdir`
No differences
`--outfile`
`--outfile`
No differences
`--packages`
`--packages`
No differences
`--platform`
`--target`
Renamed to `--target` for consistency with tsconfig. Does not support `neutral`.
`--serve`
n/a
Not applicable
`--sourcemap`
`--sourcemap`
No differences
`--splitting`
`--splitting`
No differences
`--target`
n/a
Not supported. Bun’s bundler performs no syntactic down-leveling at this time.
`--watch`
`--watch`
No differences
`--allow-overwrite`
n/a
Overwriting is never allowed
`--analyze`
n/a
Not supported
`--asset-names`
`--asset-naming`
Renamed for consistency with naming in JS API
`--banner`
`--banner`
Only applies to js bundles
`--footer`
`--footer`
Only applies to js bundles
`--certfile`
n/a
Not applicable
`--charset=utf8`
n/a
Not supported
`--chunk-names`
`--chunk-naming`
Renamed for consistency with naming in JS API
`--color`
n/a
Always enabled
`--drop`
`--drop`
n/a
`--feature`
Bun-specific. Enable feature flags for compile-time dead-code elimination via `import { feature } from "bun:bundle"`
`--entry-names`
`--entry-naming`
Renamed for consistency with naming in JS API
`--global-name`
n/a
Not applicable, Bun does not support `iife` output at this time
`--ignore-annotations`
`--ignore-dce-annotations`
`--inject`
n/a
Not supported
`--jsx`
`--jsx-runtime <runtime>`
Supports `"automatic"` (uses jsx transform) and `"classic"` (uses `React.createElement`)
`--jsx-dev`
n/a
Bun reads `compilerOptions.jsx` from `tsconfig.json` to determine a default. If `compilerOptions.jsx` is `"react-jsx"`, or if `NODE_ENV=production`, Bun will use the jsx transform. Otherwise, it uses `jsxDEV`. The bundler does not support `preserve`.
`--jsx-factory`
`--jsx-factory`
`--jsx-fragment`
`--jsx-fragment`
`--jsx-import-source`
`--jsx-import-source`
`--jsx-side-effects`
n/a
JSX is always assumed to be side-effect-free
`--keep-names`
n/a
Not supported
`--keyfile`
n/a
Not applicable
`--legal-comments`
n/a
Not supported
`--log-level`
n/a
Not supported. This can be set in `bunfig.toml` as `logLevel`.
`--log-limit`
n/a
Not supported
`--log-override:X=Y`
n/a
Not supported
`--main-fields`
n/a
Not supported
`--mangle-cache`
n/a
Not supported
`--mangle-props`
n/a
Not supported
`--mangle-quoted`
n/a
Not supported
`--metafile`
n/a
Not supported
`--minify-whitespace`
`--minify-whitespace`
`--minify-identifiers`
`--minify-identifiers`
`--minify-syntax`
`--minify-syntax`
`--out-extension`
n/a
Not supported
`--outbase`
`--root`
`--preserve-symlinks`
n/a
Not supported
`--public-path`
`--public-path`
`--pure`
n/a
Not supported
`--reserve-props`
n/a
Not supported
`--resolve-extensions`
n/a
Not supported
`--servedir`
n/a
Not applicable
`--source-root`
n/a
Not supported
`--sourcefile`
n/a
Not supported. Bun does not support stdin input yet.
`--sourcemap`
`--sourcemap`
No differences
`--sources-content`
n/a
Not supported
`--supported`
n/a
Not supported
`--tree-shaking`
n/a
Always true
`--tsconfig`
`--tsconfig-override`
`--version`
n/a
Run `bun --version` to see the version of Bun.
## JavaScript API
esbuild.build()
Bun.build()
Notes
`absWorkingDir`
n/a
Always set to `process.cwd()`
`alias`
n/a
Not supported
`allowOverwrite`
n/a
Always false
`assetNames`
`naming.asset`
Uses same templating syntax as esbuild, but `[ext]` must be included explicitly.
`ts<br/>Bun.build({<br/> entrypoints: ["./index.tsx"],<br/> naming: {<br/> asset: "[name].[ext]",<br/> },<br/>});<br/>`
`banner`
n/a
Not supported
`bundle`
n/a
Always true. Use `Bun.Transpiler` to transpile without bundling.
`charset`
n/a
Not supported
`chunkNames`
`naming.chunk`
Uses same templating syntax as esbuild, but `[ext]` must be included explicitly.
`ts<br/>Bun.build({<br/> entrypoints: ["./index.tsx"],<br/> naming: {<br/> chunk: "[name].[ext]",<br/> },<br/>});<br/>`
`color`
n/a
Bun returns logs in the `logs` property of the build result.
`conditions`
n/a
Not supported. Export conditions priority is determined by `target`.
`define`
`define`
`drop`
n/a
Not supported
`entryNames`
`naming` or `naming.entry`
Bun supports a `naming` key that can either be a string or an object. Uses same templating syntax as esbuild, but `[ext]` must be included explicitly.
`ts<br/>Bun.build({<br/> entrypoints: ["./index.tsx"],<br/> // when string, this is equivalent to entryNames<br/> naming: "[name].[ext]",<br/><br/> // granular naming options<br/> naming: {<br/> entry: "[name].[ext]",<br/> asset: "[name].[ext]",<br/> chunk: "[name].[ext]",<br/> },<br/>});<br/>`
`entryPoints`
`entrypoints`
Capitalization difference
`external`
`external`
No differences
`footer`
n/a
Not supported
`format`
`format`
Only supports `"esm"` currently. Support for `"cjs"` and `"iife"` is planned.
`globalName`
n/a
Not supported
`ignoreAnnotations`
n/a
Not supported
`inject`
n/a
Not supported
`jsx`
`jsx`
Not supported in JS API, configure in `tsconfig.json`
`jsxDev`
`jsxDev`
Not supported in JS API, configure in `tsconfig.json`
`jsxFactory`
`jsxFactory`
Not supported in JS API, configure in `tsconfig.json`
`jsxFragment`
`jsxFragment`
Not supported in JS API, configure in `tsconfig.json`
`jsxImportSource`
`jsxImportSource`
Not supported in JS API, configure in `tsconfig.json`
`jsxSideEffects`
`jsxSideEffects`
Not supported in JS API, configure in `tsconfig.json`
`keepNames`
n/a
Not supported
`legalComments`
n/a
Not supported
`loader`
`loader`
Bun supports a different set of built-in loaders than esbuild; see Bundler > Loaders for a complete reference. The esbuild loaders `dataurl`, `binary`, `base64`, `copy`, and `empty` are not yet implemented.
`logLevel`
n/a
Not supported
`logLimit`
n/a
Not supported
`logOverride`
n/a
Not supported
`mainFields`
n/a
Not supported
`mangleCache`
n/a
Not supported
`mangleProps`
n/a
Not supported
`mangleQuoted`
n/a
Not supported
`metafile`
n/a
Not supported
`minify`
`minify`
In Bun, `minify` can be a boolean or an object.
`ts<br/>await Bun.build({<br/> entrypoints: ['./index.tsx'],<br/> // enable all minification<br/> minify: true<br/><br/> // granular options<br/> minify: {<br/> identifiers: true,<br/> syntax: true,<br/> whitespace: true<br/> }<br/>})<br/>`
`minifyIdentifiers`
`minify.identifiers`
See `minify`
`minifySyntax`
`minify.syntax`
See `minify`
`minifyWhitespace`
`minify.whitespace`
See `minify`
`nodePaths`
n/a
Not supported
`outExtension`
n/a
Not supported
`outbase`
`root`
Different name
`outdir`
`outdir`
No differences
`outfile`
`outfile`
No differences
`packages`
n/a
Not supported, use `external`
`platform`
`target`
Supports `"bun"`, `"node"` and `"browser"` (the default). Does not support `"neutral"`.
`plugins`
`plugins`
Bun’s plugin API is a subset of esbuild’s. Some esbuild plugins will work out of the box with Bun.
`preserveSymlinks`
n/a
Not supported
`publicPath`
`publicPath`
No differences
`pure`
n/a
Not supported
`reserveProps`
n/a
Not supported
`resolveExtensions`
n/a
Not supported
`sourceRoot`
n/a
Not supported
`sourcemap`
`sourcemap`
Supports `"inline"`, `"external"`, and `"none"`
`sourcesContent`
n/a
Not supported
`splitting`
`splitting`
No differences
`stdin`
n/a
Not supported
`supported`
n/a
Not supported
`target`
n/a
No support for syntax downleveling
`treeShaking`
n/a
Always true
`tsconfig`
n/a
Not supported
`write`
n/a
Set to true if `outdir`/`outfile` is set, otherwise false
## Plugin API
Bun’s plugin API is designed to be esbuild compatible. Bun doesn’t support esbuild’s entire plugin API surface, but the core functionality is implemented. Many third-party esbuild plugins will work out of the box with Bun.
Plugins in Bun and esbuild are defined with a builder object.
myPlugin.ts
import type { BunPlugin } from "bun";
const myPlugin: BunPlugin = { name: "my-plugin", setup(builder) { // define plugin }, };
The builder object provides some methods for hooking into parts of the bundling process. Bun implements `onStart`, `onEnd`, `onResolve`, and `onLoad`. It does not yet implement the esbuild hooks `onDispose` and `resolve`. `initialOptions` is partially implemented, being read-only and only having a subset of esbuild’s options; use `config` (same thing but with Bun’s `BuildConfig` format) instead.
myPlugin.ts
import type { BunPlugin } from "bun"; const myPlugin: BunPlugin = { name: "my-plugin", setup(builder) { builder.onStart(() => { /* called when the bundle starts / }); builder.onResolve( { / onResolve.options / }, args => { return { / onResolve.results / }; }, ); builder.onLoad( { / onLoad.options / }, args => { return { / onLoad.results / }; }, ); builder.onEnd(result => { / called when the bundle is complete */ }); }, };
### onResolve
* options
* arguments
* results
* 🟢 `filter`
* 🟢 `namespace`
* 🟢 `path`
* 🟢 `importer`
* 🔴 `namespace`
* 🔴 `resolveDir`
* 🔴 `kind`
* 🔴 `pluginData`
* 🟢 `namespace`
* 🟢 `path`
* 🔴 `errors`
* 🔴 `external`
* 🔴 `pluginData`
* 🔴 `pluginName`
* 🔴 `sideEffects`
* 🔴 `suffix`
* 🔴 `warnings`
* 🔴 `watchDirs`
* 🔴 `watchFiles`
### onLoad
* options
* arguments
* results
* 🟢 `filter`
* 🟢 `namespace`
* 🟢 `path`
* 🔴 `namespace`
* 🔴 `suffix`
* 🔴 `pluginData`
* 🟢 `contents`
* 🟢 `loader`
* 🔴 `errors`
* 🔴 `pluginData`
* 🔴 `pluginName`
* 🔴 `resolveDir`
* 🔴 `warnings`
* 🔴 `watchDirs`
* 🔴 `watchFiles`