Regex Tester
Test regular expressions against sample text instantly.
What this tool does
Validate regular expression patterns and quickly inspect matching results using your own input text.
Tool interface
Input
Output
Example input
/\b\w{4}\b/g
This line has many word tokens in text.Example output
Pattern: /\b\w{4}\b/g
Total matches: 5
Matches:
1. This
2. line
3. many
4. word
5. textStep-by-step instructions
- Enter the regex on the first line using /pattern/flags format, or plain pattern text.
- Add the test text on the following lines.
- Click Transform to view match count and matched values.
Common use cases
- Validating extraction patterns before shipping code.
- Debugging mismatched filters in parsing pipelines.
- Comparing pattern behavior across sample input variations.
Helps developers debug and validate regex patterns before using them in code, filters, or search logic.
Common mistakes to avoid
- Forgetting regex flags such as `g` or `i` and getting unexpected matches.
- Not escaping backslashes when copying patterns between environments.
- Testing patterns on unrealistic samples that do not match production data.
Frequently Asked Questions
Can Regex Tester run patterns with flags?
Yes. Use `/pattern/flags` format, for example `/error\d+/gi`.
Why do I get zero matches in Regex Tester?
Check escaping, anchors, and flags. Small syntax differences can change matching behavior.
Can I use regex flags?
Yes. Use /pattern/flags syntax such as /test/gi.
Does it show all matches?
Yes, it reports total matches and each matched value.
Can I test multiline input?
Yes. Paste multiline content and include the `m` flag when your pattern requires it.
What input format does Regex Tester expect?
Use plain text input, usually one item per line for list-oriented tools.
What does Regex Tester output?
It returns transformed output that you can copy directly from the result panel.
Why might Regex Tester return an error?
A common issue is: Forgetting regex flags such as `g` or `i` and getting unexpected matches.
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