RegexLab
Type a pattern and some text to see matches and groups highlighted live, the pattern drawn as a diagram, patterns that could hang flagged, and a preview of any replacement. Copy it as code for five languages.
Runs in this tab. Nothing is uploaded. Keeps working if your connection drops.
- g on: every match is found, not just the first
- i off: A and a are different
- m off: ^ and $ match only at the start and end of the whole text
- s off: . matches anything except a line break
- u off: an emoji counts as two characters
- v off: no set operations in [ ]
- y off: a match can start anywhere
Start with a sample
- See the pattern as a mapA railroad diagram drawn from the pattern: every route text can take, with groups boxed in their own colour.
- Every match, part by partGroups coloured inside each match, a table of what each captured, and a step-through with [ and ].
- Safe to try anythingPatterns run in a background worker that is stopped after 2 seconds, and a safety check spots patterns that could hang.
- Take it with youReplace with a before-and-after preview, test cases that pass or fail, and code for JavaScript, Python, Go, PHP and Java.
JavaScript regex flavour. Text files up to 1 MB. Matches are found in the first 50,000 characters, up to 5,000 of them. A pattern that runs longer than 2 seconds is stopped. Nothing you type or open is saved or sent anywhere.
Pattern library
Load one to see how it works. Your text is kept if you have some.
Cheat sheet
Click a token to type it into the pattern.
