Use realistic samples
A regex can look correct on one example and fail on real text. Test matches, non-matches, blank input, extra spaces, punctuation, Unicode characters, and long strings before using a pattern in production code.
Review the pattern
- Check anchors such as ^ and $.
- Review greedy and lazy matches.
- Inspect capture groups and replacements.
- Test case sensitivity and multiline flags.
Common mistakes
Do not use regex to parse complex formats when a real parser exists. Also watch for patterns that can become slow on long input.
FAQ
Does a match mean the input is safe?
No. Regex can check shape, but it does not prove trust, ownership, or business validity.
Should I save test data?
Use harmless samples or redacted text whenever possible.