Frequently asked questions

Do I need an account?

No. You can edit and run code without one; your code is then kept in your browser only. With a free Zerethon account you also get saved projects, run history, share links and Fix Code — and more runs per day.

Which languages can I run?

Python 3.12, JavaScript (Node.js 22), TypeScript 7, Java 25, C and C++ (GCC 14), PHP 8.4, Go 1.27, Rust 1.87, Ruby 4.0, Perl 5.40, Bash 5.2, R 4.5 and SQL (SQLite 3). Every language has syntax highlighting, completion and Run tests. Format is available for all of them except Go, Rust, Ruby, Perl, Bash and R.

Is there a limit?

Each run has a time limit of 10 to 20 seconds depending on the language, plus limits on memory, processes and output. There is also a number of runs per day — lower without an account. Programs cannot use the network or install packages.

Can my program read input?

Yes — type it in the Input panel before you press Run. Typing input while the program is running is not supported yet.

How do I run tests?

Name your test files test_… (Java: …Test.java) and choose Run ▾ → Run tests. Each test file runs on its own and you see which passed or failed.

Why does my SQL say “no such table”?

Every SQL run starts from a new, empty database. Create your tables in a file under setup/ (it runs first) or put rows in data/<table>.csv. The editor can write a starting setup/schema.sql for you, or — signed in — generate the tables with sample data.

Is my code private?

Yes. Saved projects are visible only to you. Your code is sent elsewhere only when you choose: a share link shows a read-only copy, and Fix Code sends the code you selected to an AI for a suggestion you review. See the privacy policy.

What does Fix Code do?

It asks an AI, through Zerethon Workspace, to propose a fix for the selected code using its errors. You see the change side by side and decide whether to apply it; it is never run automatically.

Can I share a project?

Yes, from a saved project: Share creates a read-only link valid for 1, 7 or 30 days. You can revoke it at any time.

Where do I start?

Open the algorithms — official samples in every language, with checks — that you can open as your own project, or the public examples: short programs to try in the editor.

Something is wrong or missing

Write to hello@zerethon.com.