Online TypeScript compiler
This typechecks with the real TypeScript compiler, then runs the result. Your code never leaves this tab.
Press Run. The TypeScript 6.0 + QuickJS engine (about 2 MB) downloads once on your first run, then stays cached.
// Free tool
This typechecks with the real TypeScript compiler, then runs the result - so a type error is reported exactly as tsc reports it, with the line and the message you would see in your editor, and a program that typechecks actually executes.
Nothing you type is sent to a server. Your code is saved only in this browser, the engine is downloaded once and cached, and once it has loaded the page keeps running your code with the network off. No account, no sign-in, no limit on how many times you press Run.
// What you get
TypeScript 6.0 + QuickJS, in a browser tab
The real TypeScript compiler typechecks your code, then QuickJS runs the JavaScript it emits. Type errors are the compiler's own, word for word.
What it supports
- TypeScript 6.0 in strict mode: interfaces, generics, discriminated unions, satisfies, template literal types and the rest.
- Full typechecking before the run. If it does not typecheck, nothing executes, and the diagnostics are the compiler's own.
- The emitted JavaScript then runs in the same sandboxed engine the JavaScript tool uses.
What it does not
- Your program runs as a script, so top-level import and export have nothing to resolve against.
- No DOM and no Node types: document, window and process are absent from both the types and the runtime.
- A program is stopped after 4 seconds.
// Why it runs here
Your code never leaves the tab
Most online compilers send your code to a server, run it in a container, and send the output back. That means a queue when the site is busy, a hard cap on how long your program may run, and a copy of your code on someone else's disk. This one downloads the compiler instead, once, and runs everything locally from then on.
No upload, no account
- The compiler is fetched once and cached; your source is never sent anywhere.
- Nothing is stored on our side. Your code is kept in this browser only, so it is still here when you come back.
- Once the engine has loaded, it keeps running with the network off, which a hosted sandbox cannot do.
Then practice it for real
- A runner tells you what your code printed. It cannot tell you whether you have learned anything.
- Prepshotz runs the same engines against real test cases and grades the result.
- Practice TypeScript with graded problems →
// The other nine
Every language we run, free
// Questions
TypeScript in the browser - FAQ
01Does this actually typecheck, or just strip the types?
It typechecks. The real TypeScript compiler runs over your code in strict mode and the program only executes if it comes back clean, which is why the errors you see are word for word the ones your editor shows.
02Which TypeScript version is this?
TypeScript 6.0, the same version the graded practice uses, so a feature that works here works there.
03Does my code get uploaded anywhere?
No. The compiler runs inside your browser tab, so your code never leaves your machine. There is no server to send it to and nothing is logged on our side. Your code is kept only in this browser, and a share link carries it inside the link itself.
04Is it really free, and do I need an account?
Yes, and no. Every tool here runs without an account, a card, or a sign-in. They are free because they cost us nothing per run: the compiler is downloaded to your browser once and your own machine does the work.