Webflow only checks that an address looks valid. Here is how to confirm the mailbox actually exists, so fake, mistyped and disposable signups never reach your list, with no code or a little.
Get your API key, free Read the docs 100 free credits, no card. Works with Zapier, Make, or custom code.Setting a field to the Email type gives you HTML5 format validation, and a custom pattern can tighten it, but both only confirm the address is shaped correctly. A perfectly formatted address on a dead or disposable domain passes every native check and still bounces. To actually stop bad signups, you need a real verification step after the form is submitted.
From the built-in basics to real, deliverability-grade verification.
Set the form field to the Email type, or add a custom pattern attribute for stricter format rules.
Limitation: format only. It cannot tell whether the mailbox exists, so dead and disposable addresses still get through.
Connect your Webflow form submission to Zapier or Make. Add a step that sends the email to the Email Verifier API, then branch on the result: tag the contact, route real signups onward, and quarantine or reject invalid and disposable ones.
Secure by design: the automation calls the API server-side, so your API key is never exposed to visitors. No code required.
For full control, intercept the submit and POST the email to a small backend or serverless endpoint that holds your API key and calls the verification API, then act on the response.
Important: never put your API key in client-side JavaScript, since anyone can read it. Always call the API from your server (or use Method 2).
Verifying Webflow form emails, answered.
Only the format. Setting a field to the Email type adds HTML5 format checking, and a custom pattern can tighten it, but both only confirm the address looks valid. Webflow has no built-in way to confirm the mailbox actually exists, so format-valid but dead addresses still get through.
The simplest no-code path is automation: connect your Webflow form to Zapier or Make, add a step that sends the submitted email to the Email Verifier API, and branch on the result (tag the contact, notify your team, or skip the bad ones). For full control, call the API from your own backend or a serverless function on submit.
You can, but never put your API key in client-side JavaScript, since visitors can read it. Instead have your form post to a small backend or serverless endpoint that holds the key and calls the API, then returns the result. For a pure no-code setup, use Zapier or Make, which keep the key server-side for you.
Yes. Once the email is sent to the API, you get back invalid, disposable, role and catch-all flags, so you can reject or quarantine fake and throwaway signups before they reach your list or CRM.
Pay-as-you-go, one credit per verification, billed only for Passed and Failed results, credits never expire, and every new account starts with 100 free credits.
Grab an API key and add a verification step to your forms. 100 free credits, no credit card.
Get started freeRelated: signup form validation, verification webhooks, Typeform email verification.