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Email Format Validator

Check an email address against the rules that actually matter, and see why.

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Quick Tool Overview

The Email Format Validator checks each rule individually instead of running one huge regular expression, so a failure comes with a specific reason — and it flags the things that matter in practice, not just syntax.

What it does
Validates email syntax and explains each failure
You give it
One address or a list
You get back
A verdict with specific reasons and warnings
Best for
Debugging a form that rejects a valid address
Developer Tools Free, unlimited use No sign-up Runs in your browser

About the Email Format Validator

Email validation is usually done with one enormous regular expression that is either too strict or too loose. This checks the rules individually instead, so a failure comes with a reason rather than a bare rejection.

It checks the parts separately: the local part's length and its rules about full stops, the domain's labels and hyphens, the top-level domain, and the total length. Beyond syntax it flags what actually matters in practice — known disposable-address providers, likely typos of the common mail domains, addresses on the reserved documentation domains, and plus-addressing, which is legal and which a surprising number of forms wrongly reject.

Key features of the Email Format Validator

Reasons, not a verdict

Leading dots, double dots, over-length local parts and bad domain labels are each reported as themselves.

Typo detection

gmial.com, hotmial.com and the rest are flagged with what they were probably meant to be.

Disposable domains flagged

Known throwaway providers are identified, and the decision about whether to block them is left to you.

Plus-addressing defended

It is entirely legal, widely used, and wrongly rejected by a surprising number of forms — so it is noted rather than failed.

A normalised form

With the domain lower-cased, which is how an address should be stored and compared.

How to use the Email Format Validator

  1. 1

    Paste the address

    One address, or a list to check in bulk.

  2. 2

    Read the findings

    Each rule is checked separately and reported with its reason.

  3. 3

    Check the warnings

    Disposable providers and likely typos are flagged separately from syntax errors.

  4. 4

    Take the normalised form

    With the domain lower-cased, which is how addresses should be stored.

Frequently asked questions

No, and nothing except sending to it can prove that. Format validation catches typos and nonsense; delivery confirms existence.

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