Regex Quick Validation and Pattern Debugging
Use this page when a JavaScript-style regex needs quick validation, clearer flag handling, and a safer way to explain why the first match is right or wrong.
Stay inside the current ComUtil regex tester: it is built for JavaScript-style regexes, flag debugging, and shareable review state, not for cross-engine semantic guarantees.
Use this when
A pattern keeps matching the wrong text, the wrong amount of text, or nothing at all and you need a controlled example first.
What to inspect first
Check the active flags, first match, and capture-group output together before you rewrite the pattern.
Guardrail
This flow is for validation and explanation. It does not promise that every non-JavaScript regex engine will interpret the same pattern identically.
Email extraction
Start with a safe email example when you need to verify capture groups before you touch real logs.
\b[\w.+-]+@[\w.-]+\.\w+\b
Version string validation
Check a semantic-version style pattern before you wire it into release automation.
^v?\d+\.\d+\.\d+$
URL host parsing
Use a URL example when you need to inspect the first match and capture groups side by side.
https?:\/\/([^\/?#]+)
Many regex failures are really flag problems, so confirm g, i, m, s, u, y, d, or v usage before you decide the pattern itself is broken.
- Use each JavaScript flag once and keep the chosen flags visible in the shared state.
- Read the first match and first position before you try to interpret every highlighted result.
Presets help you validate the matching behavior without forcing private logs or customer content into the first debugging step.
- Refresh the shareable state only when the exact pattern and sample should travel to another reviewer.
- Use diff when the problem is comparing two pattern revisions rather than understanding one active pattern.