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// about this tool

Regex Tester Online

Updated 2026-07-09

Test regular expressions with live match highlighting, capture groups, and replace preview, right in your browser. Type a pattern and SnapTools highlights every match in your text as you type, breaks out captured groups, and previews substitutions. Nothing is uploaded — all matching runs locally, so it is safe for testing patterns against private or sensitive text.

Writing a regex blind and hoping it works is frustrating. The Regex Tester gives you instant feedback on what matches and what each group captures, so you can refine a validation rule, extract fields from logs, or debug a stubborn pattern in seconds.

// how to use

  1. 1 Type your regular expression in the pattern field and set flags such as g (global), i (case-insensitive), or m (multiline).
  2. 2 Paste the text to search in the input panel — matches highlight live as you type.
  3. 3 Inspect the captured groups below, and use the replace field to preview substitutions.

// examples

Match email addresses
Input
pattern: \w+@\w+\.\w+  text: contact [email protected] or [email protected]
Output
Matches: [email protected], [email protected] (2 matches)
Capture groups
Input
pattern: (\d{4})-(\d{2})-(\d{2})  text: 2026-06-29
Output
Match: 2026-06-29 — group 1: 2026, group 2: 06, group 3: 29

// common uses

Building a validation pattern for forms Extracting fields from log lines Debugging a regex that misbehaves Previewing a regex-based replacement

// faq

It uses the JavaScript regular expression engine that runs in your browser, so syntax and behavior match what you would get in JavaScript code.
g finds all matches instead of just the first, i ignores case, m makes ^ and $ match line boundaries, and s lets the dot match newlines. Toggle them next to the pattern field.
No. Matching happens in your browser — nothing is uploaded, so it is safe for testing patterns against private or sensitive text.
Regex Tester is for building and debugging a pattern with live match and group feedback; Find & Replace applies a substitution across your whole text. Use the tester to perfect the pattern, then apply it in Find & Replace.
Common causes are a missing g flag, unescaped special characters like . or (, or case sensitivity. Check the highlighted matches and group output to see what the engine is actually capturing.

↳ Curious to go deeper? Read the Regex cheatsheet with live tester guide →

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Use this via API

Get a free API key → 
curl -X POST https://snaptools.dev/api/v1/tools/regex-tester \
  -H "Authorization: Bearer YOUR_API_KEY" \
  -H "Content-Type: application/json" \
  -d '{"pattern":"pattern: \\w+@\\w+\\.\\w+ text: contact [email protected] or [email protected]"}'
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