Does the email pattern fully validate email addresses?

No. It matches the common shape of an address inside text. It does not accept every form allowed by the email standards and cannot tell whether a mailbox exists. Use it to find or pre-check addresses, then confirm by sending a message.

Why is a pattern marked as not supported in Go?

Go uses the RE2 engine, which guarantees linear-time matching and therefore has no lookahead, lookbehind or backreferences. Patterns that need those features are marked as not supported, and the flavor notes suggest checking the extra condition in code instead.

How do I open a pattern in Regex Tester?

Select the pattern and choose Open in Regex Tester. The link carries only the stable pattern id, so Regex Tester loads the pattern, its flags and sample text from the shared catalog. Nothing you type is put in the URL.

Regex Library

Tested regex patterns for every language

Search

Search patterns

Matches names, descriptions, tags and pattern text.

Regex flavor

ECMAScript RegExp in browsers and Node.js.

Patterns

46 of 46 patterns

Details

Email address in text

Extraction

Finds email-like addresses inside text such as contact lines or logs.

Intent: Finds occurrences inside longer text; it is not anchored.

Pattern

Reference pattern (JavaScript)

[a-zA-Z0-9._%+-]+@[a-zA-Z0-9.-]+\.[a-zA-Z]{2,}

Flags: g

JavaScript code

const pattern = /[a-zA-Z0-9._%+-]+@[a-zA-Z0-9.-]+\.[a-zA-Z]{2,}/g;
const matches = text.match(pattern) ?? [];

Caveats

Matches the common shape only; it does not prove the address exists or accepts mail.
Quoted local parts, IP-literal domains and internationalized addresses are not matched.
On long text without a match, backtracking engines (JavaScript, PCRE, Python, Java, .NET) can take quadratic time because each start position rescans the same characters. Limit the input length or add a timeout before running it on untrusted text.

Examples

Should match

alice@example.comMatches
Reach bob.smith+test@mail.example.org todayMatches

Should not match

alice@localhostNo match
user@exampleNo match
not an emailNo match

Examples are checked live with the JavaScript engine in your browser.

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What is Regex Library?

Regex Library is a curated, searchable catalog of tested regular expressions for validation, extraction, logs, networking, secret detection and text cleanup. Every pattern shows its intent, caveats, and examples that should and should not match, and opens directly in Regex Tester.

How to use

1.Search by name or tag, or pick a category.
2.Choose your regex flavor: JavaScript, PCRE, Python, Java, Go or .NET.
3.Select a pattern to see the variant for that flavor, its flags, caveats and examples.
4.Copy the pattern, copy it as code, or open it in Regex Tester to try your own text.

Flavors and intent labels

Patterns are written once in JavaScript syntax and checked in every flavor for lookaround, named groups, backreferences, Unicode property escapes and end-anchor behavior. Go (RE2) has no lookaround or backreferences, so those patterns are marked as not supported instead of being changed silently. Intent labels say what a pattern is for: practical validation, strict syntax, extraction, approximate detection or cleanup.

Privacy and limitations

The catalog runs entirely in your browser and makes no network requests. Examples are verified with the JavaScript engine; other flavors can behave differently where the flavor notes say so. A regex checks the shape of a value, not its meaning: it cannot prove that an email address exists, a card number is valid or a key is active.