Code & Data · Local-first
RegEx Tester Online
Test JavaScript regular expressions with highlights.
Open RegEx TesterFree · No sign-up · Browser-based processing
What RegEx Tester does
Test a JavaScript regular expression against realistic text before adding it to application code. Matches are highlighted so you can check boundaries, flags and repeated matches quickly.
Common uses
- Extract identifiers from logs
- Validate application input patterns
- Check capture behavior before using RegExp in browser or Node.js code
How to use RegEx Tester
- Paste the test text into the input field.
- Enter a pattern and optional JavaScript flags such as g, i or m.
- Run the tester and review every highlighted match and match count.
Privacy: Runs locally in your browser. Input is not uploaded to the DevNet Kit server.
RegEx Tester example
Try the tool with this representative input:
INFO started
WARN retry
ERROR connection refusedRegEx Tester FAQ
Which regex engine does this tester use?
It uses the JavaScript RegExp engine in your browser. PCRE, Python, Java and .NET expressions can behave differently.
What does the g flag do?
The global flag returns successive matches instead of stopping after the first one.
Is my test string uploaded?
No. Pattern matching runs locally in the current browser tab.