A bot fills your form and HubSpot does exactly what you built it to do: creates the contact, fires the workflow, enrols the sequence, moves the lifecycle stage. SpamKill captures every submission into quarantine, decides at 99.9% accuracy, and passes only clean submissions to HubSpot — invisible to real prospects, spam never becomes a contact, and your hidden fields, UTMs, and workflows need no changes.
Works with HubSpot embedded forms and custom posts to the Forms API — plus WordPress, Webflow, HighLevel (aka GoHighLevel), ActiveCampaign, and custom stacks.
30-day free trial, no credit card · Plans from $29/month · Cancel anytime
Only the rare flagged visitor ever sees a verification step — everyone else sees nothing, and a real person who is flagged verifies in one step and comes through. Depending on your plan, you can also review what was blocked.
Because the record doesn't just sit there — it's connected to everything you automated.
Bots don't stumble onto your forms — they hunt for them. Automated crawlers look specifically for forms wired to a CRM or marketing automation platform, because those are the submissions that produce a reaction: an autoresponder, a sequence enrolment, a sales notification. That reaction is the receipt confirming the pipe is live, and a live pipe gets revisited.
HubSpot's embedded form markup is consistent by design — that's what makes it portable across your site and your landing pages. It also makes a HubSpot form trivial to recognise at scale. Once a crawler catalogues one, the URL circulates through the lists these operations share, and the volume stops being random.
The submissions themselves have changed too. Generative tools produce filled-in forms that read like a real enquiry — a plausible company, a coherent message, a real-looking name — so the old tells of gibberish and obvious keyword stuffing catch less than they used to. The addresses tend to repeat across thousands of unrelated forms, which is exactly the pattern our public email blacklist is built from.
Three approaches teams actually use — and what each one costs.
HubSpot forms can enable CAPTCHA, and it will stop some bots. But you're adding a visible step to a form built to convert, and on paid traffic every prospect who hits that puzzle was a click you already paid for. Solver services pass CAPTCHAs for pennies, so the sophisticated submissions get through anyway — and whatever the gate turns away leaves no record at all. You cannot review a contact that was never created.
Blocked domains, email validation, exclusion lists, and a scheduled contact cleanup will all catch some junk once it's in. The problem is everything that already happened on the way in: the workflow ran, the sequence started, the rep was notified, the report absorbed it. And if the contact spent time in your billable count before anyone noticed, filtering afterwards is paying the cost and then also paying to hide it.
SpamKill sits on the form and captures each submission into its own quarantine first — not into HubSpot. There it scores how the form was filled in — timing, movement, input cadence, device signals — at 99.9% accuracy across 100M+ submissions, and passes clean submissions to HubSpot in their original format. Real prospects see nothing and hit submit. The rare flagged visitor verifies in one step and continues, so a false flag doesn't cost you the contact, while bots fail the check and never reach HubSpot at all — no record created, no workflow fired, nothing to clean. Depending on your plan, you can review the blocked queue and flag anything wrongly caught.
Swap it in during the 30-day free trial, no credit card and judge what it catches on your own traffic. Don't run a CAPTCHA and SpamKill together on the same form — your prospects get the friction of both, and the gate keeps turning real people away before anything can capture and verify them. For the full picture of how invisible detection works across any stack, see how SpamKill protects forms, or compare every approach in stopping form spam without a CAPTCHA, ranked.
Bots hunt for forms wired to a CRM, because those are the ones that produce a reaction — an autoresponder, a sequence enrolment, a sales notification. That reaction is how a crawler confirms the pipe is live and worth hitting again. HubSpot's embedded form markup is consistent and easy to recognise at scale, so once a crawler catalogues one of your forms the URL circulates and the volume compounds.
If the contacts they create are set as marketing contacts, yes — they sit in your billable count like any other record until you find and clean them. That is the part teams underestimate: junk submissions in most tools are a row to delete, but in HubSpot they can carry a recurring cost, because Marketing Hub prices by marketing contact tier. Blocking a submission before it posts is the only version of this that costs nothing.
HubSpot forms can enable CAPTCHA, and there is basic email validation and blocked-domain filtering. Those help, but a CAPTCHA adds a visible step to a form you built to convert, solver services pass CAPTCHAs cheaply, and anything the gate turns away leaves no record — a real prospect who gave up and a bot that was stopped look identical, which is to say they look like nothing at all.
SpamKill decides after capture instead of gating before it: every submission is captured into SpamKill's quarantine first, not into HubSpot. It's held just long enough to score how the form was filled in — timing, movement, input cadence, device signals — at 99.9% accuracy across 100M+ submissions, then passed to HubSpot only if it's clean. A spam submission never becomes a contact, and nothing in your workflows or campaigns changes. Real prospects see nothing and hit submit. The rare flagged visitor verifies in one step and comes straight through, so a false flag doesn't cost you the contact, and depending on your plan you can review everything that was blocked.
No. SpamKill screens the submission on the form itself and passes clean submissions through in their original format, so hidden fields, UTM parameters, and the values your workflows and lifecycle stages depend on arrive exactly as they were built. What changes is which submissions reach HubSpot at all — not what they look like when they get there. Nothing on your side needs to be reconfigured.
No — swap, don't stack. With both on the same form your prospects face the CAPTCHA anyway, so you keep exactly the friction you were trying to remove, and the gate goes on turning real people away before SpamKill can capture and verify them. The swap is safe precisely because a flagged real person can always verify straight through. Site-level bot management at your CDN works at a different layer and can stay.
Put SpamKill on the form that generates the most junk, take whatever gate is on it off, and watch what it blocks for a month. Flagged real prospects verify themselves through, so the swap doesn't cost you contacts. Thirty days, no card, from $29/month after.