Bun Runtime - Bun

Bun Runtime - BunDocumentation Index

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Skip to main contentBun home pageSearch...⌘KInstall BunSearch...NavigationCore RuntimeBun RuntimeRuntimePackage ManagerBundlerTest RunnerGuidesReferenceBlogFeedback:first-child]:!hidden peer-[.is-custom]:[&>:first-child]:sm:!hidden peer-[.is-custom]:[&>:first-child]:md:!hidden peer-[.is-custom]:[&>:first-child]:lg:!hidden peer-[.is-custom]:[&>:first-child]:xl:!hidden">Get StartedWelcome to BunInstallationQuickstartTypeScriptTypeScript 6 and 7bun initbun createCore RuntimeBun RuntimeWatch ModeDebuggingREPLbunfig.tomlFile & Module SystemFile TypesModule ResolutionJSXAuto-installPluginsFile System RouterHTTP serverServerRoutingCookiesTLSError HandlingMetricsNetworkingFetchWebSocketsTCPUDPDNSData & StorageCookiesFile I/OStreamsBinary DataArchiveSQLSQLiteS3RedisConcurrencyWorkersProcess & SystemEnvironment VariablesShellSpawnWebViewCronInterop & ToolingNode-APIFFIC CompilerTranspilerUtilitiesCSRF ProtectionSecretsConsoleTOMLYAMLMarkdownJSON5JSONLHTMLRewriterImageHashingGlobSemverColorUtilsStandards & CompatibilityGlobalsBun APIsWeb APIsNode.js CompatibilityContributingRoadmapBenchmarkingContributingBuilding WindowsBindgenLicenseOn this pageRun a file--watchRun a package.json script--bunFilteringbun run - to pipe code from stdinbun run --console-depthbun run --smolResolution orderCLI UsageGeneral Execution OptionsWorkspace ManagementRuntime & Process ControlDevelopment WorkflowDebuggingDependency & Module ResolutionTranspilation & Language FeaturesNetworking & SecurityGlobal Configuration & ContextExamplesCore RuntimeBun RuntimeCopy pagespan]:line-clamp-1 overflow-hidden group flex items-center py-0.5 gap-1 text-sm text-gray-950/50 dark:text-white/50 group-hover:text-gray-950/70 dark:group-hover:text-white/70 rounded-none rounded-r-xl border px-3 border-gray-200 aspect-square dark:border-white/[0.07] bg-background-light dark:bg-background-dark hover:bg-gray-600/5 dark:hover:bg-gray-200/5" aria-label="More actions" type="button" id="radix-_R_n4ctdbsnlht5lebsnpfdb_" aria-haspopup="menu" aria-expanded="false" data-state="closed">*]:[overflow-wrap:anywhere]">

Execute JavaScript/TypeScript files, package.json scripts, and executable packages with Bun’s fast runtime.

Copy pagespan]:line-clamp-1 overflow-hidden group flex items-center py-0.5 gap-1 text-sm text-gray-950/50 dark:text-white/50 group-hover:text-gray-950/70 dark:group-hover:text-white/70 rounded-none rounded-r-xl border px-3 border-gray-200 aspect-square dark:border-white/[0.07] bg-background-light dark:bg-background-dark hover:bg-gray-600/5 dark:hover:bg-gray-200/5" aria-label="More actions" type="button" id="radix-_R_1cctdbsnlht5lebsnpfdb_" aria-haspopup="menu" aria-expanded="false" data-state="closed">The Bun Runtime is designed to start fast and run fast. Under the hood, Bun uses the JavaScriptCore engine, which is developed by Apple for Safari. In most cases, the startup and running performance is faster than V8, the engine used by Node.js and Chromium-based browsers. Its transpiler and runtime are written in Zig, a modern, high-performance language. On Linux, this translates into startup times 4x faster than Node.js. CommandTimebun hello.js5.2msnode hello.js25.1ms This benchmark is based on running a Hello World script on Linux ​Run a file Use bun run to execute a source file. terminal

bun run index.js

Bun supports TypeScript and JSX out of the box. Every file is transpiled on the fly by Bun’s fast native transpiler before being executed. terminal

bun run index.js
bun run index.jsx
bun run index.ts
bun run index.tsx

Alternatively, you can omit the run keyword and use the “naked” command; it behaves identically. terminal

bun index.tsx
bun index.js

​--watch To run a file in watch mode, use the --watch flag. terminal

bun --watch run index.tsx

When using bun run, put Bun flags like --watch immediately after bun.

bun --watch run dev # ✔️ do this
bun run dev --watch # ❌ don't do this

Flags that occur at the end of the command will be ignored and passed through to the "dev" script itself. ​Run a package.json script Compare to npm run