Stop bad addresses at the form.

Add one line to your signup page. Every email is checked as it is typed, and the ones that would bounce are turned away before they reach your list.

Protect my form

See what your visitors see.

Three addresses, three outcomes. These are the messages the script really shows.

A typo

One click fixes it, and the form carries on.

A throwaway address

The form will not submit until it is changed.

A real address

Nothing appears. The form submits as normal.

One line, and you are done.

Create your key
It is generated for you in the app.
Paste one line
Before the closing body tag of your page.
Choose your rules
What to block, what to correct.

signup.html

  <form action="/signup">
    <input type="email" name="email">
    <button>Create account</button>
  </form>

  <script src="https://mailchecker.io/shield.js"
          data-key="vm_pub_…"></script>
</body>

You choose what is turned away.

Block undeliverable addresses

Mailboxes that do not exist, and domains that cannot receive mail.

Block disposable addresses

Throwaway inboxes that vanish before your first email.

Suggest typo corrections

gmial.com becomes gmail.com, with one click to accept.

Block free providers

Ask for a work address on forms that need one.

It fails open

If a check cannot run, the signup goes through. A problem on our side never stops a customer joining you.

Limited per visitor

Five checks an hour each by default, so nobody can use your form to hammer the checker.

Nothing to build

No framework, no package and no server code. One script tag.

Protect your next signup form.

Create an account, copy one line, and your form is protected.

Create a free account