OptiDrop

Regex Tester — Test Regular Expressions Online Free

Test and debug regular expressions with real-time pattern matching, highlighted results, and detailed match information. Supports g, i, m flags. 100% free, no sign-up.

/ / g
0 match(es) found
Matches will be highlighted here...

Match details will appear here...

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Free Regex Tester Online — Test Regular Expressions

OptiDrop's Regex Tester is a free online tool that lets you test and debug regular expressions in real time. Enter your regex pattern and test string, and the tool instantly highlights all matches, shows the match count, and provides detailed information about each match including captured groups.

How to Use the Regex Tester

Type your regex pattern in the pattern field and your test text in the textarea. Toggle the flags (global, case-insensitive, multiline) as needed. The tool automatically highlights all matching text and displays detailed match information. No need to click any button — results update instantly as you type.

Understanding Regex Flags

Regex flags modify how the pattern is interpreted. The g (global) flag finds all matches, not just the first. The i (case-insensitive) flag ignores letter casing. The m (multiline) flag makes ^ and $ match the start/end of each line. You can combine multiple flags for precise pattern matching.

Frequently Asked Questions

A regular expression (regex) is a sequence of characters that defines a search pattern. It is used for pattern matching within strings — finding, replacing, or extracting text that matches specific rules. Regular expressions are supported in virtually all programming languages and text editors.
The g (global) flag finds all matches instead of stopping at the first. The i (case-insensitive) flag makes the pattern match regardless of uppercase or lowercase. The m (multiline) flag changes ^ and $ to match the start and end of each line instead of the entire string. You can combine flags like 'gi' for global case-insensitive matching.
Enter your regex pattern in the pattern field, type or paste your test text in the textarea, and select the flags you need. The tool instantly highlights all matches in the test string and shows match details including the matched text, position, and captured groups. Results update in real time as you type.
Yes, this regex tester supports capture groups. When your pattern contains groups (parentheses), the match details section shows each captured group separately along with its value and position. This is useful for extracting specific parts of text using regex.

Last updated: June 2026