Debug JavaScript regex patterns
Test a pattern against real text, adjust JavaScript flags and see match positions without wiring up a temporary script or console snippet.
Free Tool
Regex Tester for Smarter Website Decisions
Build and debug regular expressions with live matches, flags and replacement previews.
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What It Checks
Focus Areas for This Tool
These are the signals I would review manually when deciding what needs fixing first.
01
Pattern testing
Review this area to understand whether it is helping or hurting growth.
02
Regex flags
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03
Match positions
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04
Replacement preview
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Optimization Guide
How This Tool Helps Before Publishing
A little context makes the numbers more useful. Use these notes to understand where this tool fits inside content, SEO and website reviews.
Preview replacement output
Use the replacement field to check how a find-and-replace operation will change content before applying it in code, spreadsheets or CMS fields.
Review captured groups
Each match output includes captured groups when the pattern contains parentheses, which makes extraction patterns easier to inspect.
Keep test data local
Regex matching and replacement previews run in your browser, so pasted logs, samples and draft text do not need to be sent to a server.
FAQs
Frequently Asked Questions
Quick answers about how this tool works and when to use it.
It uses the JavaScript RegExp engine available in your browser, so patterns and flags should follow JavaScript regular expression syntax.
No. Enter only the pattern text, then add flags like g, i or m in the flags field or by using the flag buttons.
Yes. Add replacement text and the tool shows the replaced output alongside the match list.
No. Matching, group extraction and replacement previews run locally in your browser.