Regex Tester

Regex Tester compiles your pattern with chosen flags (global, case-insensitive, multiline) and highlights matches, groups, and replace previews against pasted sample text.

It accelerates debugging validation rules, log parsers, and refactor-safe find patterns without bouncing between IDE and documentation.

Production regex for email or slug validation breaks on edge cases—test Unicode and plus-addressing before deploy.

Support engineers extract order IDs from messy pasted logs with iterative pattern tuning.

• Debug JavaScript form validation patterns
• Extract URLs from mixed plain-text emails
• Test grep patterns before running on production logs
• Teach capture groups in onboarding workshops
• Validate replace patterns for CMS bulk find-replace

1. 1Enter regex pattern in the pattern field.
2. 2Set flags—i for case-insensitive, g for all matches, m for multiline anchors.
3. 3Paste representative test strings including edge cases.
4. 4Review highlighted matches and numbered capture groups.
5. 5Copy working pattern into your codebase or ticket.

• Include failure cases—not just happy paths—in test text.
• Catastrophic backtracking on nested quantifiers can freeze the tab—simplify patterns on huge inputs.
• Different languages differ—JavaScript regex is not identical to PCRE in PHP.
• Pair with Text to Slug when building URL slug sanitization rules.

• Very large test strings may slow live highlighting.
• Lookbehind support depends on browser JS engine version.
• Common mistake — validating email with naive .+@.+ : use pragmatic patterns or dedicated libraries in production.