Il tester usa la stessa sintassi regex di JavaScript?

Sì, lo strumento usa il motore regex nativo di JavaScript: alcune sintassi disponibili in altri linguaggi (come i lookbehind in certe versioni di PCRE) potrebbero comportarsi diversamente.

Come vengono mostrati i gruppi di cattura?

I gruppi catturati dalla regex vengono evidenziati ed elencati separatamente dal match completo, utile per verificare che l'estrazione di sotto-parti funzioni come previsto.

Il testo che inserisco per il test viene salvato da qualche parte?

No, sia la regex sia il testo di test vengono elaborati interamente nel browser, senza essere inviati a un server.

Free Online Regex Tester — Test JavaScript Regular Expressions

Quick guide to JavaScript Regex

Regular expressions (regex) are patterns for searching, validating and transforming text. In JavaScript they're natively supported via the match(), replace(), test() and matchAll() methods.

Flags change the behavior: g finds all matches (not just the first), i ignores case, m treats each line as a string start/end, s makes the dot also match newlines.

How do I validate an email with regex in JavaScript?

A reliable email regex is /^[a-zA-Z0-9._%+\-]+@[a-zA-Z0-9.\-]+\.[a-zA-Z]{2,}$/. Regex can't guarantee 100% validity — for that you need to send a verification email.

What are capture groups?

Parentheses () create groups that capture the matching part of the text. You can reference them with $1, $2... in replace, or read them with match()[1]. Non-capturing groups use (?:...).

When to use a regular expression tester

This tool tests JavaScript regular expressions in real time, highlighting matches, captured groups, and active flags — useful during development to validate patterns before using them in code.

When to use it

You're writing a regex to validate a format (email, code, date) and want to check it against real examples before shipping it.

You need to debug an existing regex that isn't capturing the expected matches.

You want to understand how capture groups or flags (g, i, m, s) work on a concrete case.

When NOT to use it

You need to test regex in another language with different syntax (e.g. PHP's PCRE, Python's regex): this tool uses JavaScript syntax, which has some differences from other regex engines.

Alternatives

Regex tools specific to other languages (e.g. regex101.com with engine selection) when you need to test non-JavaScript syntax.

MDN's regular expression documentation to dig deeper into syntax while testing.

Common mistakes

Forgetting the "g" (global) flag when you expect to find every match in a string, not just the first one.

Not escaping special characters (. * + ? etc.) when you want to match them literally.

Writing regex that's too permissive, catching more than intended, or too strict, failing to handle valid variants of the input.

Frequently asked questions about testing regular expressions

Yes, the tool uses JavaScript's native regex engine: some syntax available in other languages (like lookbehinds in certain PCRE versions) may behave differently.

Groups captured by the regex are highlighted and listed separately from the full match, useful for checking that sub-part extraction works as expected.

No, both the regex and the test text are processed entirely in your browser, without being sent to a server.

🔍 Regex Tester