# Regex Tester & Match Debugger — Use Case Guides

For the full tool, see: [https://capytoolkit.com/tools/developer/regex-tester/](https://capytoolkit.com/tools/developer/regex-tester/)

[How to Test an Email Validation Regex](https://capytoolkit.com/tools/developer/regex-tester/test-email-validation-regex/): Paste an email pattern and a batch of real and edge-case addresses to see exactly which ones pass and which ones fail, with every match and capture group highlighted live.
[Debugging Catastrophic Backtracking Before It Ships](https://capytoolkit.com/tools/developer/regex-tester/debug-catastrophic-backtracking/): Find out whether a pattern is vulnerable to catastrophic backtracking before it reaches production, using a 500ms worker budget that catches a runaway pattern without freezing your browser.
[Testing a URL-Slug Pattern Against a Batch of Candidates](https://capytoolkit.com/tools/developer/regex-tester/test-url-slug-pattern/): Validate a lowercase, hyphen-separated slug pattern against a whole batch of candidate strings at once, using Unit Tests mode and a live pass count instead of checking each one by hand.
[Find and Replace Text Using Regex Capture Groups](https://capytoolkit.com/tools/developer/regex-tester/regex-find-replace-capture-groups/): Use Replace mode with $1 and $<name> capture-group references to reformat matched text, with a live preview that updates as you edit the pattern or the replacement template.
[Unit Testing a Regex Pattern Before You Rely on It](https://capytoolkit.com/tools/developer/regex-tester/unit-test-a-regex-pattern/): Pin a pattern down with a small regression suite of should-match and should-not-match cases, then share the whole suite as a single link a teammate can open and verify.