Online compiler, debugger and visualizer
Online Python compiler
Run Python 3.13 online with input(), several files and modules, a real debugger and a step-by-step visualizer that draws your lists, dictionaries and objects. Made for learning, practice and quick experiments.
- Free
- No sign-up
- Real compilers
- Works on phones
def fib(n): a, b = 0, 1 for _ in range(n): a, b = b, a + b return a n = int(input("How many? "))print([fib(i) for i in range(n)])What you can do
Real Python 3.13
Your code is compiled and run by the real Python toolchain on our servers, not a simulation, with the exact errors you would see on your own computer.
Input while it runs
Programs that read input (Scanner, input(), scanf, cin) ask for it in the console as they run, just like a terminal. Or prepare the input in advance.
Step-by-step debugger
Set breakpoints, step over, into and out, and watch variables and expressions change, right in the browser.
Visualizer
Replay your program line by line and see arrays, objects and the call stack drawn as it runs. Ideal for learning recursion and data structures.
Test cases
Add inputs with the expected output and run them all with one click. See which lines differ, like on a coding judge, for any code you write.
Errors explained
Compiler and runtime errors link to the exact line, with a plain-English explanation of what went wrong and how to fix it.
AI help that sees your code
Ask why a test fails or what an error means. The assistant sees your files and the real output, and can fix the right line for you.
Code together live
Share a link and code with friends or students in real time: shared cursors, edits, runs and test results.
How it works
- 1
Click "Open the Python compiler". A project with a ready-to-run main.py opens.
- 2
Write your code. Files save automatically in your browser as you type.
- 3
Press Run (Ctrl+Enter). If the program reads input, type it in the console, or press Debug (F5) to step through it.
- 4
Add test cases to check your program against expected outputs, or share a live link to code with someone.
Questions and answers
Which Python version is used?
Python 3.13.
Does input() work?
Yes. The console asks for the value while the program runs, like a terminal.
Can I import my own modules?
Yes. Create more .py files in the project and import them as usual.
Is it free?
Yes. Running, debugging, tests and live sessions are free, with no sign-up.
Where are my projects saved?
In your browser, on your device, automatically as you type. Nothing is lost when you close the tab. They stay until you delete them.
Is my code safe to run?
Every program runs in its own isolated sandbox with no internet access and strict limits on time, memory and processes, and is deleted when it finishes.