Regex tester for JavaScript patterns, matches and replacements

What is Regex Tester?

A regex tester runs a regular expression against sample text so you can inspect matches, flags and replacement behavior.

Main use case: Test a JavaScript regex pattern before using it in validation, extraction, cleanup or QA checks.

Common use cases

Form validation

Check patterns for emails, IDs, slugs or user input.

Text extraction

Extract repeated patterns from logs or copied text.

Replacement testing

Preview cleanup rules before using them in code.

How to use the tool

1. Enter a regex pattern.
2. Set JavaScript flags such as g or i.
3. Paste sample text.
4. Review matches and replacement output.

Best practices

• Use realistic test values when validating forms, exports or API payloads.
• Keep real customer, banking and production secrets out of public tools.
• Check the output format before copying it into a production workflow.
• Document whether a value is generated, validated, converted or only estimated.

Common mistakes

Confusing valid format with real-world validity

A generated or locally validated value can match a format without proving that it exists in an official system.

Using real production data

Public utilities are best for test data, demos, fixtures, QA and quick checks, not for confidential values.