Developer tools
Regex tester tool
Pattern, flags, and a subject string. Matches list with indexes; highlights in the HTML pane.
Processed in your browser — nothing is uploaded
Uses the JS RegExp engine in your browser. Invalid patterns error without wiping the subject.
Last reviewed 2026-09-10.
FAQ
Questions, answered
Which flavor?
JavaScript. Lookbehinds work in modern browsers.
Replacement?
Use Find and replace with regex enabled to rewrite.
Does my text leave the browser?
No. The regex tester runs in JavaScript on this page. Your paste is not uploaded.
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