Live JavaScript Compiler
Write and run JavaScript in your browser and see console output, warnings and errors instantly. Each run starts in a fresh, sandboxed environment. Free.
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About this tool
About Live JavaScript Compiler
Live JavaScript Compiler runs JavaScript straight in your browser, with no installs or set-up. Type or paste code, press Run Code or Ctrl+Enter, and everything your script logs appears in the console panel: console.log, info, warnings and errors, with objects and arrays printed as readable JSON and uncaught errors reported clearly. Each run starts in a fresh, sandboxed frame, so variables from a previous run never leak into the next one, and your code runs in an isolated origin that cannot read this site’s cookies or storage. Modern JavaScript works as it does in your browser: arrow functions, classes, destructuring, async/await, promises, Map and Set, and the standard library. Open the output in a new tab, expand the editor and console to full screen, copy your code or clear everything in one click. It is ideal for learning, testing a quick idea, checking how a method behaves or debugging a snippet. Nothing is uploaded.
How to use Live JavaScript Compiler
1
Write JavaScript
Type or paste code into the editor.
2
Run it
Click Run Code or press Ctrl+Enter.
3
Read the console
See logs, warnings and errors from your script.
4
Edit and re-run
Each run starts fresh, so results are always clean.
Key features
Instant results
Run code in a click or with Ctrl+Enter.
Readable console
Objects and arrays print as formatted JSON.
Fresh every run
No leftover variables between runs.
Sandboxed
Code runs in an isolated origin, away from this site’s data.
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What people run
Quick answers without opening an IDE
Learning JavaScript
Run course examples and change them to see what happens.
ExampleTry map, filter and reduce on an array.
Checking behaviour
Confirm how a method or operator really works.
ExampleTest what [] == false returns.
Interview practice
Solve coding questions and check the output.
ExampleWrite a function to reverse words in a sentence.
Data transforms
Reshape JSON or arrays for another tool.
ExampleConvert a list of objects into CSV lines.
Quick calculations
Use JavaScript as a programmable calculator.
ExampleWork out compound interest for 10 years.
Teaching
Demonstrate a concept live.
ExampleShow how promises resolve in order.
JavaScript tips
Debug faster
Log with labels
console.log('total', total) is easier to read than a bare value.
Avoid endless loops
A loop that never ends can freeze the tab; add a limit while experimenting.
Ctrl+Enter to run
Run without reaching for the mouse.
Keep your code
Code is not saved; copy it before closing the tab.
