Add email validation to Webflow forms
In Webflow, paste the widget script into Site settings, Custom code, Footer code, then add a custom attribute named data-simpleverifier to the email field of your form. The check runs in the visitor's browser and needs no API key.
Before you start
Site-wide custom code needs a paid Webflow Site plan. A page-level code box is in each page's settings.
Setup
- Open your project, then Site settings, then the Custom code tab.
- Paste <script src="https://simpleverifier.com/widget.js" defer></script> into the Footer code box (before the closing body tag) and save.
- In the Designer, select the email input inside your form. Open the Element settings panel (gear icon) and find Custom attributes.
- Add an attribute with the name data-simpleverifier and the value true. The widget only looks for the attribute, so any value works.
- Publish the site, then open the published page (not the editor preview) and type jane@gmial.com into the field. You should see a suggestion to use gmail.com under it. Try x@mailinator.com to see the disposable-address error.
<script src="https://simpleverifier.com/widget.js" defer></script>Limits on Webflow
- The widget does not run in the Designer or the editor preview, only on the published site.
- Add the custom attribute to every email field you want checked.
- Blocking a submit relies on the browser's own form validation. If a builder sends the form with its own script instead, the hint under the field still appears but the form may go through, so test on the published page.
Check that the mailbox exists
The widget checks format, typos, throwaway domains and role addresses in the browser. It cannot tell whether a mailbox exists, because that needs an API key and anything in a web page can be read by visitors. For that, call the API from the server that receives the form. See the API docs, the full form widget page with Node, PHP and Python examples, and pricing.
Common questions
- Where in Webflow does the script go?
- Site settings, Custom code, Footer code covers every page. To check one form only, use the Custom code box in that page's settings instead.
- Does it work with Webflow's built-in form submissions?
- The widget watches the email field and the form's submit event, so it works with a native Webflow form. It does not change where Webflow sends the submission.
- Can I check whether the mailbox exists?
- Not from the browser, because that needs an API key. Send the form to your own backend or to Zapier or Make and call the API there.
- Is the form widget free?
- Yes. The widget runs in the visitor's browser, needs no account or API key and has no usage limit. Checks that confirm the mailbox exists use the SimpleVerifier API from a server, which comes with Pro, Business and Agency, from $39/month.