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ConvertBox

Regex Tester

Build and debug JavaScript regular expressions with live highlighting, capture groups, and replace preview.

//
Presets:

How to Use

  1. Type a regex pattern in the top field.
  2. Toggle flags or pick a preset.
  3. Paste your test text — matches are highlighted live.
  4. Use the replace field to preview substitutions.
  5. Copy the formatted or generated result directly to your clipboard.

All processing is done in your browser, and files are never sent to a server.

Frequently Asked Questions

JavaScript's native RegExp (ECMAScript). Differences from PCRE: no recursion, slightly different lookbehind support.
Yes, syntax like (?'<name>'...) works.
No. Everything runs in your browser.
No. All operations are processed entirely inside your browser's local sandbox using client-side APIs (like WebAssembly, pdf-lib, or HTML5 Canvas). Your files and data never leave your device.
The tool is completely free with no usage limits. However, since processing occurs in your browser's memory, we recommend keeping file sizes under 50MB (especially for heavy files like PDFs or videos) to ensure stability.
No. All tools on ConvertBox are 100% free. We do not insert watermarks, limit features, or require any registration or payment.

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