Test regular expressions live in your browser. See highlighted matches, capture groups, named groups and a token-by-token explanation of the pattern.
Enter the pattern without the surrounding slashes, paste the text to test, then choose the flags. Matching happens in your browser as you type.
Do not type the surrounding slashes. A forward slash inside the pattern needs no escaping here.
As a literal —
Your text is used exactly as entered. Nothing is trimmed, because leading and trailing whitespace can change what a pattern matches.
The pattern is read token by token in your browser. A construct this reader does not model is shown as it is written, rather than described incorrectly.
Enter a pattern above to see the breakdown.
Matches, positions, capture groups and a breakdown of the pattern appear here as soon as you start typing. You can also load one of the common patterns below.
Positions are JavaScript string indices, counted in UTF-16 code units. Characters outside the Basic Multilingual Plane, such as many emoji, count as two.
This pattern found nothing in the current test string. That is a result, not an error: the pattern itself is valid.
Practical starting points, each with a sample text. They are not complete validators: real email, URL, phone and date rules depend on the system you are building, so treat these as a first draft and adjust them.
A regular expression is a pattern that describes a set of strings. Instead of searching for one fixed word you describe its shape - four digits, then a hyphen, then two digits - and the engine finds every piece of text with that shape. Regular expressions are built into almost every editor, language and command-line tool.
Type a pattern without the surrounding slashes, switch on the flags you need, and paste the text you want to test. Matching runs on every edit, so the highlighted preview, the match list and the breakdown update as you type. Nothing is submitted and nothing is saved.
Matching uses the regular expression engine built into your browser, which implements the ECMAScript specification. Other flavours are genuinely different languages: PCRE, PHP, Python, Java and .NET each add or drop syntax, so a pattern that works here may need changes elsewhere. This tool only reports what ECMAScript does.
Parentheses capture the part of the match they surround, numbered from left to right. Naming them, as in (?<year>...), makes the same capture readable in code. An optional group that did not take part in the match is reported as not matched, which is a different thing from a group that matched an empty string.
Some patterns are pathological: (a+)+$ against a long run of a characters makes the engine try an astronomical number of paths. Matching therefore runs in a background thread with a time limit. If a run exceeds it, the thread is stopped and the tester says so - the pattern is expensive, not invalid - and the next pattern runs normally.
The pattern, the flags, the test string, the matches and the captured groups stay in this browser tab. They are not sent to POLPROG, not sent to analytics or error reporting, not written into the address bar, and not stored between visits. Closing the page is all it takes to remove them.
The tester runs your pattern against your text with the browser's own ECMAScript engine and reports what it returns: matches, positions, capture groups and named groups. It does not check other regex flavours, does not measure performance, and caps the test string at 200,000 characters and the detailed match list at the first 100 matches so a large result stays readable. The total number of matches is still reported in full.
No. Everything runs in your browser: the pattern, the flags, the test string, the matches and the captured groups stay in the page. This tool has no API call, writes nothing to storage, and sends none of it to analytics or error reporting.
The ECMAScript engine built into your browser, the same one that runs JavaScript regular expressions. PCRE, PHP, Python, Java and .NET are different flavours with different syntax and different behaviour, so a pattern verified here is verified for JavaScript only.
Matching runs in a background thread with a time limit of about one second. A pattern such as (a+)+$ on a long input can take effectively unlimited time; when the limit passes the thread is stopped and the tester reports that execution was stopped. The pattern is expensive, not invalid, and the next pattern you type runs normally.
An optional group that never took part in the match has no value at all, which is different from a group that matched an empty string. JavaScript reports the first as undefined and the second as an empty string. The tester keeps them apart because the distinction changes what your code has to handle.
Axios became the default HTTP client for many JavaScript teams because it offered a clean API before Fetch became the standard browser primitive. Today, many teams can use native Fetch directly or pick Ky, a small wrapper that adds convenience without the full weight of Axios. The right choice depends on whether you actually need Axios-specific features such as interceptors and existing wrappers, or whether a lighter, more modern request layer fits your app better.
TypeScript vs JavaScript: Which Should You Use for Frontend?
TypeScript and JavaScript compared
JavaScript is the language of the web, and TypeScript is JavaScript with a type system that helps teams catch mistakes earlier and maintain larger codebases with more confidence. For small scripts and quick prototypes, plain JavaScript may be enough. For serious frontend applications, TypeScript often pays for itself through better tooling, safer refactors, and clearer contracts between modules. The right choice depends on project size, team experience, and how long the code needs to live.
Lodash is one of the most widely used utility libraries in the JavaScript ecosystem, especially in older and enterprise codebases. es-toolkit is a modern alternative built around TypeScript, ES modules, tree-shaking, and smaller bundles. The question is not whether Lodash still works. It does. The better question is whether your project still needs the weight and legacy patterns that come with it, or whether a leaner, type-first option fits your stack better in 2026.
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