Regex Tester — Test Regular Expressions Free

Test regex patterns against any text with live match highlighting. See all matches, groups, and positions. Free, no signup.

How to Use Regex Tester

Enter InputType or paste your input data into the tool interface

ProcessClick the action button to run the tool

Use OutputCopy or download the result for your project

Regex Tester — Free Developer Utility

Regex Tester — test and debug regular expressions against any text with instant match highlighting. Regular expressions are powerful pattern-matching tools used in every programming language, but they are notoriously difficult to write and debug mentally. A regex tester lets you iterate on your pattern in real time, seeing exactly which parts of the text match. Our tool supports common flags: case-insensitive matching (i), multiline mode (m) where ^ and $ match line boundaries, and dotall mode (s) where dot matches newlines. All matches are shown with their positions, making it easy to verify your regex works correctly before adding it to your code. Supports JavaScript regex syntax which is compatible with most modern languages.

Keywords and Search Terms

Developers searching for this tool use terms like: regex tester, test regex, regular expression tester, regex pattern, regex match. Tooliby provides this utility free with no signup, no watermarks, and no data logging.

Privacy — Your Data is Never Stored

Every input you paste into Tooliby developer tools is processed in memory and immediately discarded. We do not log inputs, store results, or analyze your data. Your code, tokens, API keys, and sensitive strings stay completely private.

Frequently Asked Questions

The regex tester uses .NET RegEx which is compatible with most common regex patterns. Standard quantifiers (+, *, ?, {n,m}), character classes ([a-z], \d, \w), anchors (^, $), and groups are all supported.

Flag 'i' makes the regex pattern case-insensitive. Flag 'm' enables multiline mode where ^ matches the start of each line. Flag 's' (dotall) makes . match newline characters in addition to all other characters.

Use ^ at the start and $ at the end of your pattern with the multiline (m) flag. For example, ^\d{3}-\d{4}$ matches lines that contain exactly a phone-number-like pattern.

Parentheses () in a regex pattern create a capture group that extracts specific parts of the match. For example, (\d{4})-(\d{2}) captures the year and month separately from a date string.

Some regex features differ between implementations. Python uses re syntax while .NET uses a slightly different flavor. Lookaheads, lookbehinds, and named groups have minor syntax differences. Check the specific feature in both docs.