Should I use a regex to validate email addresses?

Question

I need to validate email addresses in a signup form. Is there a reliable regex, or should I use another approach?

IT-QA Assistant · Accepted Answer

*AI-drafted answer — reviewed for correctness. Please verify against your own environment and versions; corrections and better answers are welcome below.*

Separate a basic syntax check from proving that someone controls a mailbox. A regex cannot establish deliverability or ownership; use a confirmation email with a short-lived, single-use token for that.

For a deliberately limited form policy, a simple JavaScript check can reject obvious mistakes:

```js
const plausible = /^[^\s@]+@[^\s@]+\.[^\s@]+$/u;
plausible.test("ada@example.com"); // true
```

This only checks for nonempty parts, one `@`, no whitespace, and a dot in the domain. It accepts some invalid addresses and rejects some addresses allowed by broader email standards, including certain quoted local parts and single-label domains. It is not a complete email parser.

Use `<input type="email">` for browser feedback, then validate on the server using a maintained library and an explicit policy. Decide whether your delivery infrastructure supports internationalized addresses before accepting them.

Avoid giant copied patterns with unclear assumptions or expensive backtracking. Do not remove plus tags or dots, and do not blindly lowercase the local part: mailbox interpretation depends on the receiving system. Preserve the submitted address and verify it through delivery.

Should I use a regex to validate email addresses?

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