About this tool
What is the Regex Tester?
Paste a regular expression and a test string — get live match highlighting, capture group breakdown, replace preview, and a plain-English explanation of what the regex matches. Supports JavaScript regex flavor (the most common) with all flags (g, i, m, s, u, y).
Developers use this for debugging complex patterns before pasting into code. Data analysts use it for extracting fields from log lines. Writers use it for find-and-replace operations.
FAQ · REGEX TESTER
Questions about the Regex Tester
Which regex flavor is supported?
JavaScript / ECMAScript regex — the same flavor used in JS, TS, and most modern languages. Most patterns translate directly to PCRE (Python, PHP, Perl) but some advanced features differ. The explainer notes when a feature is JS-only.
Does it explain what my regex does?
Yes — a plain-English breakdown shows what each piece of the pattern matches (character classes, quantifiers, lookarounds, captures). Useful for learning regex or auditing one someone else wrote.
Free?
Yes — runs in-browser, no signup, no character limit on the test string.