Test your regular expressions with live match highlighting. This free regex tester online shows matches in real time, lists capture groups, and counts results, all inside your browser with zero data sent to any server.
A regex tester is a tool that lets you write a regular expression pattern and immediately see how it matches against a test string. This regex tester online highlights every match in real time, lists capture groups, and reports the total match count. It runs entirely in your browser, so nothing is sent to a server and your data stays private.
The g (global) flag finds all matches instead of stopping at the first one. The i (case-insensitive) flag makes the pattern match regardless of letter casing, so /abc/i matches "ABC". The m (multiline) flag changes ^ and $ to match the start and end of each line rather than the entire string. You can combine any of these flags together.
Capture groups are portions of a regex pattern enclosed in parentheses. When the pattern matches, each group captures the substring that matched its sub-pattern. For example, the pattern (\d{4})-(\d{2})-(\d{2}) applied to "2026-03-18" creates three groups: "2026", "03", and "18". This tool displays all capture groups for every match so you can verify your extraction logic.
Yes. This regular expression tester runs entirely in your browser using JavaScript. Your patterns and test strings are never transmitted to any server. You can verify this by watching the Network tab in your browser's developer tools, no requests are made when you type or test patterns. This makes it safe for testing patterns against sensitive data like log files, emails, or configuration values.