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Build regex with confidence.

Q: Which JavaScript regex flags should I use?

Use g to find every match, i for case-insensitive matching, and m when ^ and $ should work on each line. The workspace also supports s for dot-all, u for Unicode-aware matching, and y for sticky matching.

Q: How do I match an exact value?

Wrap the pattern with ^ at the start and $ at the end. For example, ^hello$ matches hello only, not hello world or say hello. Escape any special characters that should be treated literally.

Test, inspect, and ship regular expressions without an account. Every keystroke stays on your machine.

Instant matchingPrivate by defaultBuilt for JavaScript

live workspace

Your expression, explained.

Engine JavaScript (ECMAScript)

02Test string

0 chars

match output

Matches

0 matches

debugger

live

See what the engine sees.

CompileReady

Execution time0.00 ms

Backtracking riskLow

The expression will run locally when you type.

plain-language explanation

What this pattern does.

pattern library

Ship from a trusted starting point.

Verified JavaScript patterns for the validation work your team repeats most.

58verified patternsJavaScript

Showing 12 of 58 patternsClick any pattern to load it into the workspace.

regex guide

A faster way to build, test, and understand regex.

Regex is a free workspace for turning a fuzzy pattern idea into a reliable expression. Use it as a regex tester while you are exploring, then keep it open as a practical reference when the pattern becomes part of your application, script, or CI validation.

Use this regex tester before code reaches production

A regular expression can look small while carrying a lot of behavior. A missing anchor, an overly broad character class, or the wrong flag can change the result for every user input. This regex tester runs directly in your browser, so you can paste realistic examples, see each match and capture group, and adjust the expression without creating an account. The live output is especially useful for log parsing, form validation, extraction tasks, and text cleanup.

Start with the pattern field and test string, then compare the visible match positions with what you expected. Turn flags on or off to see how global, case-insensitive, multiline, dot-all, Unicode, and sticky matching affect the result. When a pattern is invalid, the regex checker surfaces the JavaScript error immediately instead of leaving you to guess why the expression did not run.

Part regex cheat sheet, part regex builder

The pattern library works like a concise regex cheat sheet for common development jobs. Load a starter for an email address, HTTP URL, ISO date, UUID, IPv4 address, semantic version, JSON property, or repeated whitespace. Each example includes test data and the appropriate flags, which makes it easier to understand the pattern in context. Treat these starters as building blocks: change the character classes, anchors, groups, or quantifiers until they match the rules your product actually needs.

If you need a regex generator, this workspace gives you a more dependable path than a one-click black box. Build the expression in small pieces, inspect what each piece matches, and keep a representative set of accepted and rejected samples in the test area. The plain-language explanation and capture-group output help turn symbolic syntax into decisions your team can review. When you are ready, copy the expression or create a shareable link that restores the same pattern, flags, and test string.

Regex 101 for JavaScript and grep-style searches

For a quick regex 101 refresher, remember that literals match themselves, character classes such as [A-Z] define alternatives, and quantifiers such as +, *, and {2,4} control repetition. Parentheses create groups, while ^ and $ anchor a pattern to a line or string. These parts combine quickly, so test every assumption with examples that include the edge cases you do not want to match.

Developers searching for grep regex guidance can use the same core pattern thinking here, with one important caveat: regex flavors differ. This tool validates JavaScript (ECMAScript) expressions, including named groups and JavaScript flags. A pattern that works in grep, PCRE, or another language may need small syntax changes before it works in browser code. Use the engine feedback and the match list to catch those differences early.

Private, fast, and free for everyday pattern work

Regex is designed for the small, repeated moments of developer work: checking a validation rule, extracting data from a payload, reviewing a teammate’s pattern, or teaching a new hire how a group behaves. It also works well for quick one-off investigations. Every keystroke stays in your browser, the core regex tester is free, and no signup stands between you and the result. Keep this page nearby whenever you need a focused regex builder, cheat sheet, generator, or checker that makes the next expression easier to trust.

regex FAQ

Common regex questions, answered.

Use these quick explanations as a starting point, then test each idea in the live workspace above.

What is regex?

Regex, short for regular expression, is a compact pattern language used to find, validate, extract, or replace text. A pattern describes the shape of text you want to match, such as an email address, date, identifier, or repeated whitespace.

How do I test a regex?

Enter a pattern and a representative test string in the workspace. Review every match, its position, and any capture groups. Include both examples that should match and edge cases that should not.

Which JavaScript regex flags should I use?

Use g to find every match, i for case-insensitive matching, and m when ^ and $ should work on each line. The workspace also supports s for dot-all, u for Unicode-aware matching, and y for sticky matching.

How do I match an exact value?

Wrap the pattern with ^ at the start and $ at the end. For example, ^hello$ matches hello only, not hello world or say hello. Escape any special characters that should be treated literally.

How do capture groups work?

Parentheses capture part of a match so you can inspect or reuse it. Named groups such as (?<year>\d{4}) make the captured value easier to identify in the match output and in JavaScript code.

Why is my regex not matching?

Check the test input, character case, anchors, escaping, and flags first. A pattern may also use syntax from a different regex flavor. This tool checks JavaScript expressions, so PCRE or grep patterns may need adjustment.

How do I match special characters literally?

Escape regex metacharacters with a backslash. For example, use \. for a period, \+ for a plus sign, and \? for a question mark. Put a backslash in the test field only when the text itself contains one.

Is it safe to share a regex link?

Share links contain the current pattern, flags, and test text in the URL. Do not include passwords, tokens, personal data, or other sensitive values, because anyone with the link can read them.

Why does a regex work in one tool but not another?

Regex flavors differ. This workspace uses JavaScript (ECMAScript), while grep, PCRE, Python, and other tools can support different syntax, flags, and Unicode behavior. Re-test the pattern in the target environment before shipping.

built into the workspace

Less guessing. More shipping.

Regex keeps the practical context close: match groups, execution feedback, a plain-language breakdown, and templates that solve the common cases.

Private workspace Nothing is sent to a server.

Safer iteration Catch invalid syntax and risky nested quantifiers early.

Share when ready Generate a URL for the current expression.