FoxGuard form protection
Real-Time Email Validation Widget for Your Signup Forms.
One script tag puts our 9-point engine behind every form on your site. Catches bad emails as visitors type.
Try the exact check FoxGuard runs on your forms:
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The plain-English version
What a real-time email validation widget actually does
An email validation widget is a small script that watches the email fields on your site and verifies each address the moment a visitor types it. Not the cosmetic check your form library already does, which only confirms the text contains an @ and a dot. FoxGuard sends the address through Verifox’s full email verification service: syntax against RFC 5321/5322, domain and MX record existence, a live SMTP handshake with the receiving mailbox, disposable-domain and role-address detection, and catch-all resolution with AI-confidence scoring. The verdict comes back in about 380 milliseconds and the form reacts before the visitor hits submit.
The alternative is cleaning up afterwards, and afterwards is expensive. A typo like gamil.com becomes a welcome email that bounces, a trial that never activates, and a contact your sales team chases for nothing. Disposable addresses skew every conversion metric you report. And catch-all domains, which accept mail for any address whether the mailbox exists or not, are where 20 to 40% of B2B lists quietly rot. You can scrub all of this later with a bulk email validator, but the cheaper fix is refusing the bad address while the person who typed it is still looking at the field.
Install is deliberately boring: paste one script tag, pass your API key, done. The widget finds every email input on the page on its own, works with whatever built your forms, and needs no backend changes. Want to spot-check an address by hand first? The free email checker runs the identical engine, 4 checks a day, no account. Wiring validation deeper into your stack happens through the REST API, with pay-as-you-go credits and volume pricing shown for your region.
Add email validation to any form
Three steps between your current form and one that refuses fake addresses. Most teams finish before their coffee does.
Generate your API key
Create a free account and grab a key from the dashboard. Signup comes with 1,000 verification credits, 2,500 if you use a work email, and no card.
Paste one script tag
Drop the snippet into your site's head and pass your key to Verifox.init. No backend changes, no build step, no framework adapter.
Every form validates in real time
FoxGuard finds each email input on the page and verifies what visitors type as they type it. Invalid and disposable addresses get flagged before submit.
<script src=“https://api.verifox.ai/v1/widget/widget.js”></script>
<script>
Verifox.init({
apiKey: “foxkey_your_full_key”,
blockDisposable: true,
});
</script>Works with React, Next.js, Webflow, WordPress, Framer, Shopify, HubSpot embeds, and plain HTML. If an email input renders on the page, FoxGuard guards it.
What FoxGuard catches before submit
Every keystroke-level verdict comes from the same verification engine that scored 99.99% accuracy on our 1,000-address benchmark.
Malformed addresses
Full RFC 5321/5322 syntax validation, far stricter than the regex in your form library. Typos like gamil.com and missing TLDs never reach your database.
Domains that cannot receive mail
Domain existence and MX record checks confirm there is actually a mail server behind the address before you accept the signup.
Dead mailboxes
A live SMTP handshake pings the mailbox itself. The domain can be real while the inbox is long gone; FoxGuard tells the difference.
Disposable domains
Throwaway services like Mailinator are matched against a continuously updated disposable-domain list and rejected with a message you control.
Role addresses
info@, admin@, and sales@ signups rarely belong to a person. Flag them, block them, or let them through; the policy is one config switch.
Catch-all gambles
Catch-all detection plus AI-confidence scoring resolves the domains that accept everything, where 20 to 40% of B2B lists silently fail.
Two more signals round out the nine: domain age, because a domain registered last Tuesday behaves differently from one with a decade of history, and the sender’s SPF, DKIM, and DMARC posture. Together they feed the confidence score attached to every verdict, so a borderline address arrives labeled as borderline instead of pretending to be a clean pass.
Stop bad emails at the door
A bad address that enters your funnel costs you three times: the bounce, the sender-reputation hit, and the cleanup later. FoxGuard removes all three at the only moment the visitor can still fix the typo.
99.99%
accuracy on our 1,000-address benchmark
~380 ms
median verification, sub-50 ms when cached
20-40%
of B2B lists fail at catch-all domains
2.1B+
emails verified by the Verifox engine
Sender reputation is the quiet casualty of unvalidated forms. Mailbox providers track the bounce rate of everything you send, and a signup flow that accepts fake addresses feeds that rate every day. Once the score slips, even legitimate mail starts landing in spam, and digging out takes months. If your domain has already taken hits, run an email blacklist check to see where you stand, then let FoxGuard keep the new damage from ever starting.
Enterprise-grade security and scale
FoxGuard runs on the same SOC 2 Type II audited infrastructure as the Verifox API. Every address is processed in memory and discarded after the verdict: never stored, never logged, never sold.
SOC 2 Type II
Independently audited to the SOC 2 Type II standard.
GDPR
Built for the EU with full GDPR data-subject rights.
CCPA
California opt-out, do-not-sell, plus DSAR handling.
ISO 27001
Information security held to the ISO 27001 standard.
ISO 42001
AI governance aligned to the new ISO 42001 standard.
Widget questions
Ten straight answers
What developers and growth teams ask before putting an email validation widget in front of their signups, answered with the real numbers and the real limits.
Does the email validation widget slow down my signup form?
No. The script loads deferred, so it never blocks your page render, and validation runs while the visitor is still typing. Median verification latency is around 380 ms, with cached results returning in under 50 ms. By the time someone reaches the submit button, the verdict is already in. Full performance details live in the API documentation.
How does FoxGuard block disposable email addresses?
Every address a visitor types runs through the same 9-point email verification engine behind our API, and one of those checks is a continuously updated disposable-domain match. Throwaway services like Mailinator get flagged the moment the domain appears, and you choose whether FoxGuard rejects the address outright or shows a custom message asking for a real one.
Does the widget work with React, Webflow, HubSpot, and WordPress forms?
Yes. FoxGuard attaches to any HTML email input on the page, regardless of what generated it: React and Next.js apps, Webflow, WordPress, Framer, Shopify, HubSpot embeds, or hand-written HTML. No plugin or framework adapter needed. If you build forms entirely in JavaScript and want direct control, the REST API exposes the same checks as plain endpoints.
Do I need backend code to use FoxGuard?
No. The whole integration is one script tag with your API key. The widget calls Verifox directly from the browser, so there is nothing to deploy, no server to patch, and no webhook to maintain. Teams that also want server-side enforcement on submit can re-verify through the email verification API, but the widget alone stops the bad address at the form.
What does the FoxGuard free tier include?
Signing up free gives you 1,000 verification credits, or 2,500 if you sign up with a work email. No card required. Each widget check uses one credit, credits never expire, and when you outgrow the free batch, volume pricing is pay-as-you-go and shown for your region.
What happens when a visitor types an invalid email?
FoxGuard flags the input inline, before the form submits. You decide the behavior per verdict: hard-block invalid and disposable addresses, show a configurable warning for risky catch-all ones, or simply highlight the field and let the visitor correct the typo. Every message is customizable, and the verdicts mirror what the free email checker returns: valid, invalid, or risky.
Is the widget GDPR-safe? Do you store the emails visitors type?
Addresses are processed in memory and discarded the moment the verdict returns. Nothing is stored, logged, or sold, which keeps your data-processing story short for GDPR review. Verifox is SOC 2 Type II audited, and the privacy policy spells out exactly what we touch. Your visitors’ emails stay your visitors’ emails.
Can FoxGuard catch catch-all domains?
Yes, and that matters more than most teams expect: 20 to 40% of B2B email lists fail at catch-all domains, the check most free tools skip. FoxGuard runs catch-all detection plus an AI-confidence pass on every ambiguous address, the same resolution our bulk email validator applies to uploaded lists. You get a usable verdict instead of a shrug.
Can I customize which checks block and what messages visitors see?
Yes, everything is config on the init call. Toggle whether disposable addresses are rejected, whether free providers like Gmail are allowed on B2B forms, whether invalid inputs get highlighted, and the exact message shown for each verdict, in your choice of language. The defaults are sensible, so most teams ship the two-line snippet first and tune the policy from the dashboard once real signups flow.
How is FoxGuard different from the free email checker?
Same engine, opposite direction. The free email checker is for addresses you already have: paste one in, get a verdict. FoxGuard validates addresses as they arrive, automatically, on every form. If you are prospecting and need addresses you do not have yet, the email finder covers that side, and AI agents can call everything through our MCP server.
Start free
Put FoxGuard on your forms this afternoon
Sign up, copy your key, paste the script tag. You get 1,000 free verification credits to start, 2,500 if you use a work email, and no card is required. Credits never expire, so whatever your forms do not use this month is still yours next year.
Get 1,000 free creditsVolume pricing for bigger traffic is on the pricing page, localized to your region.