Codemod Runner
Batch-transform code with pattern rules and preview the diff
Runs 100% in your browser — nothing is ever uploaded.
What is Codemod Runner?
Rename an API across a file, swap import styles, or migrate deprecated calls in seconds. Paste your code, define one or more pattern → replacement rules (plain text or regex with capture groups), and preview every change as a unified diff before you apply it. Everything runs locally in your browser — your source code never leaves your machine.
How to use Codemod Runner
- Paste the source code you want to transform.
- Add one or more rules: a pattern (text or /regex/) and its replacement — $1, $2 capture groups work.
- Click Preview to see a unified diff of every change.
- Apply the rules and copy or download the transformed code.
Frequently asked questions
What is a codemod?
A codemod is an automated, repeatable code transformation — like renaming a function everywhere or migrating an old API call to a new one. Instead of error-prone manual editing, you define the rule once and apply it across the whole file consistently.
Does it support regular expressions?
Yes. Wrap the pattern in slashes (like /console\.log\((.*?)\)/) to enable regex mode, and use $1, $2 in the replacement to reuse captured groups. Plain-text patterns are matched literally.
Is my source code uploaded anywhere?
No. The transformation engine is pure JavaScript running inside your browser tab. Your code never touches a server, which makes the tool safe for proprietary and confidential codebases.
Is my code uploaded to a server?
Never. Every CodeKit tool runs entirely in your browser with JavaScript. Your code is processed on your device and never touches a network — it even works offline once the page is loaded.
Are these tools really free?
Yes — 100% free, no sign-up, no limits, no watermarks. We keep the site running with minimal, non-intrusive ads.
Is there a file or size limit?
No hard limit. Because processing happens on your machine, the only constraint is your device’s memory. Files of several megabytes work fine.