Regex Tester

Free Online Regex Tester

Need to check whether a regular expression actually matches what you think it matches? Our free online Regex Tester lets you write a pattern, paste a test string, and see every match highlighted instantly, entirely inside your browser. Toggle flags, view a full list of matches with their exact position in the text, and copy your results with one click. No software to install, no sign-up, and no text ever uploaded to a server.

Whether you’re validating an email format, extracting data from a block of text, or debugging why a pattern isn’t matching the way you expect, this tool turns the usual trial-and-error into something you can watch happen live. If you need to evaluate the length or structure of your input text prior to testing, you can also use our Word Counter, adjust capitalization with the Case Converter, or calculate line breakdowns using the Line Counter.

See Exactly What’s Matching, and Where

Rather than just telling you whether your pattern matches or not, this tool shows you precisely which parts of your text matched, highlighted directly in context, plus a detailed breakdown for each individual match. Every entry in the match list shows the matched text itself along with its exact start and end position in the string, so you know exactly what your pattern is picking up and can quickly spot false positives or missed matches.

Instant Feedback on Every Keystroke

Both your pattern and your test string are watched in real time. Change a single character in your regex, and the highlighted matches update immediately, no button to click, no page to reload. If your pattern has a syntax error, like an unmatched parenthesis or an invalid quantifier, the status bar shows a specific, readable error message right away instead of a vague failure.

Who Uses This Regex Tester?

This tool is useful anytime you need to build, check, or debug a regular expression, including:

• Developers: Validating input formats like emails, phone numbers, or postal codes before writing them into application code. For related development workflows, you might also want to quickly encode/decode parameters with our URL Encoder Decoder, clean up server responses using the JSON Formatter, or safely hash text strings via the Hash Generator.
• Data analysts: Testing a pattern for extracting specific values, like URLs, dates, or IDs, from a block of scraped or logged text. If your data requires formatting modifications or filtering before extraction, utilities like the Extra Spaces Remover and Text Sorter can prepare it instantly.
• QA engineers: Verifying that a validation pattern correctly accepts valid input and rejects invalid input before it ships.
• Students learning regex: Watching matches light up in real time as they experiment with different tokens and quantifiers, which is often the fastest way to build an intuitive understanding of how each piece behaves. If you just need random dummy text to experiment on, you can generate it instantly using our Lorem Ipsum Generator.
• System administrators: Testing a pattern intended for log filtering or search before deploying it in a script or configuration file. If you are handling text records containing epoch times, parsing them through our Unix Timestamp tool can make interpretation much simpler.
• Anyone debugging a broken pattern: Quickly narrowing down whether an issue is a missing flag, an escaping problem, or a logic error in the pattern itself.

What Makes This Tool Different

Regex101 and RegExr are excellent, feature-rich tools with capture group explanations, substitution testing, multi-language engine support, and saved community pattern libraries, and they’re genuinely strong choices for deep regex work across PCRE, Python, and other engines. This tool takes a lighter, more focused approach for a specific need:

If you need capture group breakdowns, substitution and replace testing, multi-language regex engine support, or a library of saved community patterns, a more full-featured tool like Regex101 or RegExr will serve that deeper workflow better. This tool is built for quickly writing, checking, and confirming a pattern without the extra overhead.

JavaScript Regex Engine

This tool runs on the native JavaScript (ECMAScript) regex engine, the same engine used by browsers and Node.js. Most patterns port directly to other common engines like PCRE or Python’s re module, though some advanced features, such as lookbehind assertions and certain Unicode property classes, can behave differently across engines. If your pattern is destined for a non-JavaScript codebase, it’s worth a quick check against that specific engine’s documentation for any edge-case differences. If you are dealing with other structured text documents altogether, you can effortlessly visualize them using our Markdown Preview or translate numbers using the Binary Converter.