01
Enter your regex pattern
Type or paste your regular expression into the pattern field, without the surrounding slashes, to start matching right away.
Regex Tester Online
Test, debug, and validate your regular expressions in real-time. Extract capture groups, count matches, and check syntax errors instantly.
Developer Tool
Regex Tester Online
//gi
Flags:
Matches List0 matches
No matching elements found. Adjust regex pattern or test string to see matches.
100% Secure & Private
Processed locally in your browser. No data is sent to our servers.
How to use
Use this regular expression tester in three simple steps
Our workflow is designed to be straightforward, allowing you to complete your task in seconds.
02
Set flags and add test text
Toggle flags like global or ignore-case, then paste the sample text or code you want to run the pattern against.
03
Review matches and groups
Read the highlighted matches, match count, and captured groups that update live, then refine your pattern until it fits.
Live Highlights
Colors matched strings visually in your target text.
Regex Flags
Support for global, case-insensitive, and multiline toggles.
Match Extraction
Extracts grouped matches into an easy-to-read list format.
Local Evaluation
Tests expressions locally to prevent regex denial of service.
Use cases
Useful for different workflows
Input Validation
Verify regex patterns for form validation like email or phones.
Web Scraping
Test custom capture group expressions before running scrapers.
String Replacement
Deconstruct match matches for editor search-replace rules.
Tool guide
What is a Regular Expression?
A regular expression (regex or regexp) is a sequence of characters that forms a search pattern. When you search for data in text, you can use search patterns to describe what you are looking for. It can be a single character, or a more complicated pattern used for validation, string parsing, or search-and-replace tasks.
Understanding Common RegExp Flags
Flags are optional parameters added to a regex pattern to modify its search behavior. The most common flags are:
- g (global): Does not return after the first match; instead, searches for all occurrences in the target string.
- i (ignoreCase): Makes the expression case-insensitive.
- m (multiline): Alters ^ and $ to match the beginning and end of lines, rather than only the entire string.
How to Test Regex Expressions
Type your regular expression inside the top text box and paste your code or text block in the test text area. Our matching engine updates automatically as you type, indicating matches, offsets, and matched group structures. It processes everything client-side, making it highly secure for test logs and raw code segments.
FAQ
Frequently asked questions
What language engine does this regex tester use?
This regex tester uses your browser's native JavaScript regular expression engine (V8 on Chrome/Edge, SpiderMonkey on Firefox, and JavaScriptCore on Safari). It supports standard JavaScript regex syntaxes.
Can this regex tester cause browser freezing?
If you write a regular expression susceptible to catastrophic backtracking (e.g. nested quantifiers like `(a+)+` against long mismatch strings), the browser tab might freeze. This is a characteristic of native regex execution. Ensure you write clean patterns.
How do capture groups work?
By placing parts of your regex pattern in parentheses `( )`, you create capture groups. Our tester dynamically lists the characters captured by these parentheses for every matched string in the outputs.
Is my private text data stored or saved on your servers?
No, your text is processed entirely in your browser's temporary memory. We do not store, track, or share any of your inputs.
Which regex flags can I toggle?
You can switch on global, ignore-case, multiline, dotall, and unicode flags and instantly see how each one changes the matches in your test string.
From our blog
Test Your Regex Without the Guesswork
Read the full guide behind the Regex Tester Online and get the most out of it.
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