Invisible regex behavior
Highlighted spans make greedy quantifiers, anchors, and escaped characters easier to verify.
Free Developer Tool
Regex Tester Highlight Matches and Capture Groups
Debug a pattern against real text in real time. Toggle global, case insensitive, multiline, and dotAll flags, then inspect every match, group, count, and position without uploading data.
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Regex Tester Problems Developers Avoid
Make regular expressions visible before they reach code, logs, validation rules, or production data.
Missing capture details
Capture groups appear beside each match, making parsers, validators, and extraction scripts easier to debug.
Unsafe paste workflows
Private logs, emails, API responses, and test strings can be checked locally in the browser.
Regex Tester Features for Daily Debugging
Live highlighting, flags, capture groups, positions, match counts, and templates sit in one focused tool.
Live match highlighting
Highlighted spans update as soon as the pattern, flags, or test text changes.
Flag controls
Toggle global, case insensitive, multiline, and dotAll flags without rewriting the regex literal.
Capture group inspector
See numbered and named capture groups for each match, including positions when the browser supports match indices.
Match count and positions
Review total matches, full match text, and start-end offsets for quick parser debugging.
Common templates
Load email, URL, phone, date, and IP address regex templates with sample text in one click.
Private local processing
The JavaScript RegExp engine runs in your browser and does not upload pasted text.
How to Use Regex Tester
The workflow follows the short debug loop developers use all day: paste, toggle, inspect, and refine.
01
Enter your regex
Paste only the pattern body, then use the flag toggles to control global, case insensitive, multiline, or dotAll matching.
- Paste only the pattern body, then use the flag toggles to control global, case insensitive, multiline, or dotAll matching.
02
Paste test text
Add logs, validation examples, sample input, or copied content. Matches highlight immediately.
- Use realistic positive and negative examples so the pattern is not too broad.
03
Inspect matches and groups
Review the count, start-end positions, full match text, and capture groups before copying the final pattern.
- Review the count, start-end positions, full match text, and capture groups before copying the final pattern.
Regex Tester Workflows
Use this workflow for validation, extraction, and quick pattern reuse without switching tools.
Highlight live matches
Watch each matched span update while you refine anchors, quantifiers, and character classes.
Debug capture groups
Inspect every match with numbered groups, named groups, and start-end positions.
Start from templates
Load email, URL, phone, date, and IP address patterns, then adapt them to your project.
Regex Tester Use Cases
Useful wherever pattern correctness matters before code ships.
Form validation
Test email, URL, phone, date, and ID validators before wiring them into a frontend form.
Log parsing
Extract IDs, timestamps, paths, and error messages from copied logs with visible match positions.
Content cleanup
Find repeated patterns, unusual separators, and structured snippets before writing replacement code.
Regex Tester FAQ
Common questions about flags, capture groups, matching behavior, and privacy.
What does Regex Tester show?
It highlights matches, counts them, shows start-end positions, and lists capture groups for each match.
Does Regex Tester upload my text?
No. Matching uses the browser JavaScript RegExp engine, so pasted text is processed locally.
Which flags are supported?
Regex Tester supports global, case insensitive, multiline, and dotAll flags through simple toggles.
Can Regex Tester show capture groups?
Yes. Numbered and named capture groups appear for every match, with positions when supported by the browser.
Start Using Regex Tester
Paste a pattern and sample text, choose flags, then inspect highlighted matches, capture groups, counts, and positions.
Free forever - browser-only regex tool.