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Python Tutor
by Python Tutor
What Python Tutor is
Python Tutor is a free web tool that runs code and shows its execution step by step. Visualizations can display variables, objects, pointers, data structures, and stack frames. Supported languages are Python, Java, C, C++, and JavaScript. The site describes uses for students debugging coursework, teachers explaining programming concepts, and programmers preparing for interviews. Created by Philip Guo in 2010, it runs code in a backend sandbox without file or network access. Python, Java, and JavaScript runs are limited to 1,000 steps; C and C++ runs allow about 300. Python execution is restricted to a whitelist of common standard-library modules. The tool does not support multi-file projects, package installation beyond that whitelist, or visualization of JavaScript event-loop and asynchronous behavior. Visualizations can be embedded in another webpage with an iframe. Teachers and student teaching assistants may apply for free ad-free mode and added teacher features, subject to manual eligibility verification.
Who it suits
It suits learners, educators, and interview candidates who need visual explanations of short programs in supported languages.
What it does well
- Free web access
- Supports five programming languages
- Shows execution state step by step
- Embeddable visualizations
- Teacher ad-free mode application available
What to know first
- No file or network access
- Execution step limits apply
- No multi-file projects
- Python modules are restricted
Plans
| Plan | Billed and limits | Price |
|---|---|---|
| Free | Free to use · Python, Java, C, C++, and JavaScript visualization | Free |
As pythontutor.com lists them, read 9 Oct 2026. The maker's own page has the final word.
Verdict
Python Tutor provides language support and visual execution tracing without a subscription. Its sandbox and project limitations make it better for focused examples than unrestricted development.
Facts from Python Tutor's own pages
- Creator
- The site says Python Tutor was created by Philip Guo in 2010. · pythontutor.com, 9 Oct 2026
- Embedding
- The site documents embedding a visualization in another webpage using an iframe. · pythontutor.com, 9 Oct 2026
- Execution limits
- The documented execution sandbox has no file or network access and limits runs to 1,000 steps for Python, Java, and JavaScript and about 300 for C and C++. · pythontutor.com, 9 Oct 2026
- Founded
- 2010 · pythontutor.com, 28 Sept 2026
- Free plan
- Yes · pythontutor.com, 20 Sept 2026
- Intended users
- The site describes uses for students debugging coursework, teachers explaining concepts, and programmers preparing for interviews. · pythontutor.com, 9 Oct 2026
- Languages
- The site supports Python, Java, C, C++, and JavaScript. · pythontutor.com, 9 Oct 2026
- Other limits
- The site guide says it does not support multi-file projects, package installation beyond the Python whitelist, or JavaScript event-loop and asynchronous visualization. · pythontutor.com, 9 Oct 2026
- Purpose
- Python Tutor lets users write code in a web browser and see a step-by-step visualization as it runs. · pythontutor.com, 9 Oct 2026
- Python limits
- Python execution is limited to a whitelist of common standard-library modules. · pythontutor.com, 9 Oct 2026
- Support
- The homepage links to a bug-report form and documentation on unsupported features. · pythontutor.com, 9 Oct 2026
- Teacher access
- Teachers and student teaching assistants can apply for free ad-free mode with added teacher features, subject to manual eligibility verification. · docs.google.com, 9 Oct 2026
- Visualizations
- It visualizes variables, objects, pointers, data structures, and stack frames. · pythontutor.com, 9 Oct 2026
Where Python Tutor stands on Freedom251
- Coding Playgrounds#58 of 138
- Code Playground Software#39 of 58