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Regex Checker

Check regex syntax and inspect matches in a browser-based testing workspace.

2 matches2 groups1 ms
161 chars

Uses your browser's JavaScript regex engine. Matching runs in a background thread, so a runaway pattern is stopped instead of freezing the page. Need a pattern from a plain English description? Try Regex AI, also offline

Matches with their position and capture groups
#MatchPosition
1
user
ada.lovelace8-20
domain
example.com21-32
8-32
2
user
support+billing80-95
domain
mail.example.co.uk96-114
80-114

Working with Regex Checker

Use concrete examples to find mistakes in a pattern's boundaries and character classes. Inspect captures and match locations before relying on the expression. A successful match against one sample is only the beginning of testing.

How to use Regex Checker

  1. Enter a regular expression and select its flags.
  2. Paste representative matching and non-matching text.
  3. Inspect highlighted matches, groups, and replacement behavior when needed.

Regex Checker example

Check a product-code pattern against valid codes, incomplete codes, and strings with extra leading or trailing characters.

What to expect from the result

The checker does not prove that a pattern is safe for every input or efficient at production scale. Avoid testing pathological expressions against very large strings.

Regex Checker questions

How do I use Regex Checker?

Enter a regular expression and select its flags. Paste representative matching and non-matching text. Inspect highlighted matches, groups, and replacement behavior when needed.

What should I check in the result?

The checker does not prove that a pattern is safe for every input or efficient at production scale. Avoid testing pathological expressions against very large strings.

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