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Regex Tester
Write a regular expression and see every match highlighted in your test text as you type, with capture groups broken out and a plain-English breakdown of what each part of the pattern does. Toggle the flags, check replacements, and catch a catastrophic-backtracking pattern before it hangs something in production.
gim
3 matches
Highlighted
Reach us at ada@jcit.systems or grace@example.org. Old address ada@lovelace was retired in 2018.
Capture groups · first match
- Group 0 (whole)
- ada@jcit.systems
- Group 1
- ada
- Group 2
- jcit.systems
- <user>
- ada
- <domain>
- jcit.systems
Result
Reach us at ada [at] jcit.systems or grace [at] example.org. Old address ada [at] lovelace was retired in 2018.
Method & assumptions
- This is the JavaScript regular-expression engine (the one in your browser), so PCRE-only constructs like lookbehind quirks or recursion may differ.
- Without the g flag, only the first match is highlighted and only the first replacement is made — the same behaviour your code would see.
- Zero-length matches (say from a* or an empty pattern) are marked with a thin caret; matching is capped so a runaway pattern cannot hang the tab.
- Everything runs in your browser. The pattern and text you enter are never sent anywhere.
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Software engineering
We write the software
behind tools like these
Anyone building a pattern and tired of guessing why it matches everything or nothing.
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