If you use forms to collect leads, you know the pain: fake signups, weird emails, and spam that clogs your pipeline. If you’re using HubSpot Forms, there are built-in tools and settings that can help, but most people barely scratch the surface. This guide is for marketers, admins, and anyone tired of chasing ghosts in their CRM. Let’s dive into what really works, what’s a waste of time, and how to lock things down—without making life miserable for real people.
Why spam and fake submissions happen (and why it matters)
Spambots hammer web forms all day, often just for kicks or to build email lists. Sometimes, it’s humans submitting junk data to get your lead magnet. Either way, you end up with:
- Dirty CRM data
- Wasted sales time
- Skewed analytics
- Annoying follow-ups to people (or bots) who never cared
The good news: With a few changes in HubSpot, you can block 90% of this stuff without expensive plugins or custom code.
Step 1: Turn on reCAPTCHA (and why you should)
reCAPTCHA is the single most effective spam blocker built into HubSpot Forms. It throws up a roadblock for bots, but real users barely notice it.
How to enable reCAPTCHA in HubSpot Forms
- Go to your HubSpot account and click the gear icon (Settings).
- In the left sidebar, navigate to Tools > Marketing > Forms.
- Find the Spam Prevention section.
- Flip on the switch for reCAPTCHA.
Heads up:
- HubSpot uses an “invisible” reCAPTCHA, so it won’t annoy most visitors.
- Some bots can get past older CAPTCHAs, but Google’s version is still solid.
Pro tip:
If you’re using embedded forms on a custom site, double-check that your site isn’t blocking Google’s reCAPTCHA scripts. Some privacy plugins or aggressive ad blockers can break it.
Step 2: Use email validation (but don’t expect miracles)
HubSpot lets you require a valid email format (e.g., user@example.com). It’s something, but it won’t stop someone from typing “asdf@asdf.com” or a throwaway Gmail.
How to set up email validation
- In your form editor, click the email field.
- In the sidebar, make sure “Email” is set as the field type.
- Check “Make this field required.”
- Optionally, enable “Block free email providers” if you only want business emails (see below).
What works:
- Stops most bots that don’t bother with proper formatting.
- Catches obvious typos.
What doesn’t:
- Won’t stop determined spam or fake signups.
- Blocking free email providers (like Gmail, Yahoo) can annoy real leads, especially in B2C or small business.
My take:
Use required email and format validation—always. Blocking free providers? Only if you’re 100% B2B and ready to lose some legit leads.
Step 3: Add custom field logic (but keep it simple)
You can use “progressive fields” or custom questions to trip up bots and lazy spammers. For example, ask a question that only a real person would answer correctly.
Ideas for custom fields
- Add a simple text question: “What color is the sky?” (Answer: blue)
- Or a math question: “2 + 2 = ?”
- Use dropdowns with answers bots can’t guess easily.
How to add a validation question
- Add a single-line text or dropdown field to your form.
- Make it required.
- For basic validation, set acceptable answers (in form logic or workflows).
What works:
- Blocks most bots, who just fill in junk or leave it blank.
- Can catch lazy humans, too.
What doesn’t:
- Overcomplicated questions frustrate real users.
- Smart bots can sometimes parse predictable questions.
Pro tip:
Switch up the question every few months. Don’t overthink it—just make it something a bot can’t guess.
Step 4: Use hidden honeypot fields (advanced, but effective)
A honeypot is a hidden field that real users never see. Bots, though, fill out every field—so you can filter out any submission where this field isn’t blank.
HubSpot’s limitation:
HubSpot Forms doesn’t have built-in honeypot functionality, but you can fake it:
How to add a honeypot (basic workaround)
- Add a text field with a label like “Leave this field blank.”
- Hide it with CSS (
display: none;). - Set up a workflow to trash or flag any submission where this field isn’t empty.
What works:
- Catches basic bots.
- Doesn’t annoy real users at all.
What doesn’t:
- Not bulletproof. Smarter bots look for hidden fields.
- Requires a tiny bit of manual setup and workflow logic.
Pro tip:
Name the field something boring (not “honeypot”) so bots don’t get suspicious.
Step 5: Block obvious spam email domains
Some email domains are used only by spammers or bots. You can block these manually.
How to block specific email domains
- In your form, select the email field.
- Use the “Blocklist” or “Validation” option to enter domains you want to reject (e.g.,
mailinator.com,tempmail.com).
What works:
- Cuts down on throwaway and temporary email addresses.
What doesn’t:
- There are always new disposable domains popping up.
- Risk of blocking some legit people if you get overzealous.
Pro tip:
Start with the big offenders. Update your list monthly if spam picks up.
Step 6: Use double opt-in or email confirmation (if you’re serious)
Double opt-in means a user has to click a link in their email before they’re added to your list. It’s not for everyone, but it kills most fake signups.
How to set up double opt-in in HubSpot
- Go to Settings > Marketing > Email.
- Click the Double Opt-In tab.
- Enable double opt-in and customize your confirmation email.
What works:
- Stops almost all fake and bot signups.
- Cleans your list, improves deliverability.
What doesn’t:
- Adds friction—some real users never confirm.
- Not ideal for urgent lead capture or high-volume sales funnels.
My take:
Use it if you care more about quality over quantity. For early-stage startups or contests, it’s probably overkill.
Step 7: Review and clean up submissions regularly
No matter what you do, some junk will sneak through. Set aside time each week or month to review submissions and look for:
- Suspicious patterns (same IP, weird domains)
- Gibberish in names or companies
- Sudden spikes in submissions
What works:
- Keeps your CRM clean.
- Helps you spot new spam trends.
What doesn’t:
- It’s manual work, but you can automate parts with HubSpot workflows.
Pro tip:
Set up a workflow to auto-flag submissions with certain keywords, domains, or field patterns for review.
What to ignore (or at least not stress about)
- Third-party spam plugins: Most don’t play nice with HubSpot Forms or are redundant if you use the steps above.
- Blocking by IP: Too easy for spammers to rotate addresses. Not worth the hassle unless you’re facing a targeted attack.
- Making every field required: Just makes real users angry. Only require what you actually need.
Wrapping up (Keep it simple, iterate as you go)
You don’t need a hundred plugins or a PhD in cybersecurity to stop most spam in HubSpot Forms. Start with reCAPTCHA, use smart field logic, block the worst offenders, and keep an eye on your data. Most important? Don’t overcomplicate your forms—real people hate jumping through hoops. Tweak and test as you go. You’ll stay ahead of the spammers without driving away the leads you actually want.