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Regex Tester Online
Test JavaScript regular expressions against sample text.
Experiment with JavaScript-compatible regular expressions and inspect every match. Paste the input, make the change, then read the result before you copy it elsewhere.
Test edge cases, not just one happy-path example.
Ready — input is processed locally.
This utility runs on the current device for the supported workflow. Kaazo does not need the pasted input to calculate the result.
The useful scope of Regex Tester
Experiment with JavaScript-compatible regular expressions and inspect every match.
A match is only as good as the test cases
One successful example doesn’t prove a regular expression is safe for every input. Test expected matches, expected failures and edge cases such as empty strings, line breaks or repeated delimiters.
A pattern that works on one sample can still backtrack badly or match unexpected input in production. Test edge cases, not just the happy path.
Don’t ask Regex Tester to do a different job
Don’t use a regex as a full parser for a structured language when a real parser exists.
FAQ
What does Regex Tester actually do?
Experiment with JavaScript-compatible regular expressions and inspect every match.
What is the easy mistake to make here?
One successful example doesn’t prove a regular expression is safe for every input. Test expected matches, expected failures and edge cases such as empty strings, line breaks or repeated delimiters. A pattern that works on one sample can still backtrack badly or match unexpected input in production. Test edge cases, not just the happy path.
Does formatted or converted output prove the data is valid for my application?
No. Regex Tester can perform the syntax or data operation described here, but your application can still impose its own schema, business rules, encoding or security requirements.
Related tools
After Regex Tester, validate the output before feeding it into another transform. The data-format guide has broader context if you need it.