Ruby Runner
Free online Ruby runner. Write and run Ruby 3.4 code instantly in your browser with puts output, real error messages and an example library. Nothing to install.
Which Ruby version does this runner use?
It runs the official CRuby 3.4 interpreter compiled to WebAssembly (the ruby.wasm project). After the engine loads, the badge next to the header shows the exact version reported by RUBY_VERSION.
Does my code leave my device?
No. The whole interpreter runs inside your browser tab via WebAssembly, so parsing, execution and output all happen locally. Nothing is uploaded to any server and no account is needed.
Why is the first load around 30 MB?
You are downloading a complete Ruby interpreter together with its standard library. Your browser caches it after the first download, so later visits start almost instantly without fetching it again.
Can I use the standard library or gems?
The standard library is included, so require "json", "set", "date" and friends work out of the box. Installing third-party gems is not possible because the runtime is fully offline by design.
What happens if my script runs forever?
A run is stopped after about 10 seconds and the engine restarts automatically, so the page never freezes. This limit makes the runner ideal for snippets and exercises rather than long-running jobs.
How is this different from installing Ruby locally?
There is zero setup: it works on any device including phones and Chromebooks. For real projects with files, network access, gems or long jobs, a locally installed Ruby remains the better tool.
Are puts, print and p supported?
Yes. Standard output appears in the output panel, stderr and raised exceptions are shown in red with the class, message and line number, just like in a terminal.
Can I read user input with gets?
No. Scripts run non-interactively with stdin closed, so gets returns nil immediately. If you need interactive input, run the same code with a local Ruby interpreter.
Is there a keyboard shortcut to run the code?
Yes. Press Ctrl+Enter (Cmd+Enter on Mac) inside the editor to run the current code without touching the mouse.
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