Online Code Debugger
A powerful, free online debugger for JavaScript, Python, C++, and Java. Set breakpoints, step through code line by line, inspect variables, and watch the call stack — all in your browser.
Debugger Features
Breakpoints
Click any line to set a breakpoint. Execution pauses exactly where you need it, letting you inspect the full program state.
Step Over / Step Into
Step through your code one line at a time. Step over function calls or step into them to trace the full execution path.
Variable Inspector
See all variables in scope, their current values, and types. Watch them change as you step through the code.
Why Use an Online Debugger?
Setting up a local development environment just to debug a small snippet is overkill. Code Visualizer's online debugger lets you paste any code and start debugging immediately — no IDE, no plugins, no configuration.
It's perfect for technical interviews, studying algorithms, debugging code from Stack Overflow, or helping a friend understand why their code doesn't work.
Supported Languages
Debug JavaScript, Python, C++, and Java — all from the same interface. Switch languages with one click and the debugger adapts automatically.