Practical email address regex
A deliberately practical email check for forms that require one @ sign, a dotted domain, and no whitespace.
^[^\s@]+@[^\s@]+\.[^\s@]+$Open breakdown →REGEX TERMINAL / JS RUNTIME
Regexplain
Decode, test, and understand JavaScript regular expressions without leaving the browser.
LOCAL SYNTAX MAPLIVE MATCH TESTEROPTIONAL AI SUMMARY
QUICK LOAD
Local tools stay in this browser. Your pattern is sent to Groq only when you request an AI summary.
Local syntax mapDETERMINISTIC
Enter a pattern to inspect its syntax locally.
Select a token to read its description.
Matches will be highlighted here.
PROCESS / 03 STEPS
How It Works
Start with deterministic browser tools. Add an AI explanation only when you want another layer of context.
Enter the source
Paste the pattern without surrounding slash delimiters, then add flags in their own field.
Inspect it locally
Read the syntax map, select individual tokens, and test sample text directly in your browser.
Ask for context
Request an optional plain-language AI summary when the deterministic tools are not enough.
RUNTIME / JAVASCRIPT
JavaScript regex, clearly scoped.
Regexplain targets the JavaScript / ECMAScript regular-expression flavor and compiles patterns with the browser runtime. That makes the local tester useful for the environment where your front-end code will actually run.
A successful match is evidence about text shape, not truth. Regex validates format, not meaning or strength; business rules, deliverability, security, and real-world existence need separate checks.
MANUAL / FAQ
Before you run the pattern
- What regex flavor does Regexplain use?
- Regexplain uses the JavaScript / ECMAScript RegExp flavor. Syntax support follows the browser runtime that opens the page, so newer features depend on that browser.
- Should I include slash delimiters?
- No. Enter the pattern without surrounding slash delimiters. Put flags such as g, i, m, s, u, v, or y in the separate flags field; any slash typed in the pattern remains literal content.
- Is my regex processed privately?
- The syntax map and sample testing run locally in your browser. If you request an AI summary, Regexplain sends your pattern and flags to its server and then to Groq for that response.
- What can regex validation tell me?
- It can tell you whether the pattern and flags form valid JavaScript syntax and whether sample text matches. Regex validates format, not meaning or strength, so it cannot prove that an email exists, a password is strong, or a URL is safe.
LIBRARY / 05 PATTERNS
Start with a checked-in example
Practical patterns with explicit tradeoffs, test strings, and common mistakes.
Password format regex
A password format check requiring lowercase, uppercase, and a digit across 12 to 64 allowed characters.
^(?=.*[a-z])(?=.*[A-Z])(?=.*\d)[A-Za-z\d@$!%*?&]{12,64}$Open breakdown →US phone number regex
A North American-style phone check with an optional +1 country code, paired area-code parentheses, and common separators.
^(?:\+1[ .-]?)?(?:\(([2-9]\d{2})\)|([2-9]\d{2}))[ .-]?([2-9]\d{2})[ .-]?(\d{4})$Open breakdown →HTTP and HTTPS URL regex
A conservative web URL check for HTTP(S), dotted hostnames, and an optional path, query, or fragment.
^https?:\/\/(?:www\.)?[a-z0-9](?:[a-z0-9-]*[a-z0-9])?(?:\.[a-z]{2,})+(?:[/?#][^\s]*)?$ [flags: i]Open breakdown →CSS hex color regex
A CSS-oriented hex color check accepting 3-, 6-, or 8-digit notation with an optional leading #.
^#?(?:[0-9a-f]{3}|[0-9a-f]{6}|[0-9a-f]{8})$ [flags: i]Open breakdown →