Online Java Compiler
Write Java and compile it in the browser. Your class must be called Main, and compiler errors come back exactly as javac reports them — which is usually the fastest way to see what went wrong.
Running code needs a free account. Write and edit here as much as you like — pressing Run asks you to sign in. It is free, takes about a minute, and covers all five languages plus graded exercises.
Create free accountHow this Java compiler works
Compiled with a real JDK 21 (javac) in an isolated container on our servers, then run. It is the actual compiler, not a simulation, so the diagnostics are the ones you would get locally.
Frequently asked questions
Why must my class be called Main?
The file is saved as Main.java before compiling, and Java requires a public class to match its filename. Rename your class to Main and it will compile.
Which Java version?
Java 21 (Eclipse Temurin JDK), so modern syntax like records, switch expressions and text blocks all work.
Is this Java compiler really free?
Yes — free, with no card and no trial. It needs a free account, because running code costs real server time and an account is how we keep that fair for everyone. Signing up takes about a minute.
Do I need to install anything?
No. Everything runs on our servers and the results come back to your browser. Nothing to download, no setup, works on a phone.
Can I use this for interview practice?
Yes, and there are graded exercises with hidden test cases if you want feedback rather than just output — those need a free account.
Want feedback, not just output?
A free account unlocks graded exercises — you write a solution, it runs against hidden test cases, and you are told exactly which ones fail and why. Plus structured courses in Java and 17 other paths.
Create a free account