TypeScript Playground

How to write, type-check and run TypeScript online for free?

Use AnyTool's TypeScript Playground: type TypeScript in a CodeMirror editor and it live-compiles to JavaScript, type-checks against the full bundled lib.d.ts, and runs the emitted JS in a sandboxed iframe with a console. The TypeScript compiler is self-hosted and runs in a Web Worker, so 100% in your browser - no upload, no signup.

Live type-checking with the complete DOM + ESNext lib.d.ts - real errors, line and column
See compiled JavaScript for any target, module or JSX setting and copy or download it
Run code in a sandboxed iframe and stream console.log, errors and async output
100% in your browser - no upload, no signup, works offline

What is

An in-browser editor that compiles TypeScript to JavaScript, type-checks it against the standard library, and runs the result so you can experiment with code without installing anything.

Developer Tools

Related terms

TypeScript compiler (tsc)tsconfig compilerOptionslib.d.ts type definitionsJavaScript transpilation

Frequently Asked Questions

No. AnyTool bundles the TypeScript compiler and the lib.d.ts files locally and runs them in a Web Worker. There is no backend and no runtime CDN, so your source is compiled, type-checked and executed entirely on your device and works offline.

No. The compiler is self-hosted and runs in a Web Worker, so your code never leaves the browser tab.

Yes. Pressing Run (or Ctrl+Enter) emits JavaScript and executes it inside a sandboxed allow-scripts iframe. It captures console.log, console.warn, console.error, thrown errors and async output and streams them into a DevTools-style console, with an 8 second watchdog that terminates runaway loops.

Yes. It compiles to JavaScript and runs it in a sandboxed iframe, streaming console output into a console pane.

No. To keep everything client-side with no runtime CDN, the playground does not resolve arbitrary npm imports such as lodash or react from a registry. You get the full DOM and ESNext standard library and your own code, but external package imports are out of scope.

No. Resolving arbitrary npm imports needs a network or server, which would break the no-upload promise.

Quick controls in the toolbar set the target (ES3 through ESNext), module format and strict mode, plus a .tsx toggle with JSX options. The tsconfig tab exposes a live JSON editor and checkboxes for flags like noImplicitAny, strictNullChecks and esModuleInterop, all of which drive the compiler instantly.

Use the Target and Module dropdowns and the strict toggle, or edit the tsconfig JSON tab directly.

Detailed Explanation

Technical Details

How AnyTool TypeScript Playground compiles and type-checks in the browser

The playground self-hosts the official TypeScript compiler and its lib.d.ts files and loads them into a Web Worker. As you type, it runs an in-memory language service over the source for genuine type diagnostics and uses ts.transpileModule to emit JavaScript. Because the compiler is bundled rather than fetched from a CDN, the whole pipeline works offline.

Uses the real TypeScript compiler, not a regex type-stripper
Full DOM + ESNext lib.d.ts is bundled locally
Compiler runs in a Web Worker so typing stays smooth
Builds are debounced about 250ms for live updates

Methodology

Running emitted JavaScript safely

Pressing Run compiles the code and executes the emitted JavaScript inside a throwaway iframe with sandbox set to allow-scripts only. Console output, thrown errors and async results are sent back via postMessage that is validated by the iframe source and a per-build id. An 8 second watchdog terminates the frame to guard against infinite loops.

Execution is isolated in a sandboxed allow-scripts iframe
allow-same-origin is never granted to the run frame
8 second timeout kills runaway loops
Captures log, warn, error and unhandled rejections

Privacy & Security

Client-side privacy and its honest limits

Everything happens on your device: no backend, no API, no telemetry, and snippets are shared through a pako-compressed URL hash rather than a server. The trade-off is that arbitrary npm imports cannot be resolved without a network, so external packages such as lodash or react are out of scope while the full standard library is supported.

No upload, no signup, no project cap, works offline
Sharing encodes code and config in the URL hash, not a server
Arbitrary npm package imports are not resolved
Supports DOM and ESNext standard-library types only

AnyTool TypeScript Playground vs typical online alternatives
Capability	AnyTool	Typical alternative
Privacy / no upload	Yes - 100% client-side	Often server-side execution
Runtime CDN required	No - compiler is self-hosted	Often loads compiler from a CDN
Works offline	Yes	Usually no
Signup / project cap	None	Common (paywalls, 3-project caps)
Run + console output	Yes - sandboxed iframe	Sometimes JS-emit only
Full lib.d.ts type-checking	Yes - DOM + ESNext	Sometimes a compact lib
Price	Free	Freemium / paywall

Several rivals marketed as in-browser actually run code on servers or microVMs.