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Add a CAPTCHA to a sign-up form created in Brevo

We strongly recommend using a CAPTCHA confirmation in your forms to protect against bot attacks and spam signups, which can result in issues such as fake data being added to your lists. If you are creating your sign-up form in Brevo, you can choose between Google reCAPTCHA or Cloudflare Turnstile CAPTCHA.

Good to know

What is a CAPTCHA?

A CAPTCHA is a security feature used in forms to distinguish between human users and bots. It typically presents a challenge that is easy for humans to solve but difficult for bots, such as identifying distorted text, checking a box, selecting specific images, or solving simple math problems.

Here's an example of what the Google reCAPTCHA (v2) with the "I'm not a robot" checkbox looks like:

CAPTCHA gif example

❗️ Important
We recommend you always include a CAPTCHA in your forms, such as the Google ReCAPTCHA v3 or Google reCAPTCHA v2 with the "I'm not a robot" checkbox.

What is the difference between Google reCAPTCHA and Cloudflare Turnstile CAPTCHA?

Google reCAPTCHA and Cloudflare Turnstile CAPTCHA are both tools designed to prevent bots from submitting forms and interacting with websites. The following table shows a comparison of the two to help you decide which one to use:

  Google reCAPTCHA Cloudflare Turnstile CAPTCHA
Provider Google Cloudflare
Integration Widely used across the web. More commonly used among websites using Cloudflare services for broader security needs.
Type of verification Requires users to interact with a checkbox or invisible challenge to confirm they are human. Provides customizable challenges based on detected bot behavior.
Ease of use Generally easy to implement with straightforward setup instructions. Seamlessly integrated for websites using Cloudflare services.
Cost Free for most users, but Google may collect data from users to improve its services. Included with Cloudflare’s service plans, which vary in pricing based on features and usage.

Step 1: Create your CAPTCHA

Start by creating your preferred CAPTCHA:

Create a Google reCAPTCHA Create a Cloudflare Turnstile CAPTCHA

To create a Google reCAPTCHA:

  1. Log into your Google account or create a new one.
  2. Go to the reCAPTCHA admin console at this link: https://www.google.com/recaptcha/admin/create.
  3. Enter an internal name for your reCAPTCHA in the Label field.

  4. Select the reCAPTCHA type you want to use:

    reCAPTCHA type User interaction Advantages Disadvantages
    Score based (v3) Always invisible, working silently to detect bot behavior without user interruption. Provides enhanced security without disrupting the user experience. Requires careful implementation to interpret scores correctly and take appropriate actions based on those scores.
    reCAPTCHA (v2) - "I'm not a robot" Checkbox Always requires users to click a checkbox to confirm they are human. Simple for users and effective against most bots. Can sometimes interrupt the user experience with additional verification steps, such as image-based challenges.
    reCAPTCHA (v2) - Invisible reCAPTCHA badge Typically runs invisibly but can prompt a challenge when necessary. Reduces user interaction while still being able to prompt challenges when suspicious activity is detected. Can occasionally interrupt the user experience with additional verification steps if the system detects potentially suspicious behavior.

  5. Fill in the Domains field depending on how you plan to share your form: 

    ❗️ Important
    If you are not sure which domain applies to your setup, add bothsibforms.com and your-website-domain.com. This works for all form sharing methods and prevents the most common CAPTCHA errors.
    How you plan to share your form Domain to add Form type
    Quick Share link sibforms.com Standard sign-up form
    Embedded Iframe sibforms.com Standard sign-up form
    Embedded HTML your-website-domain.com (e.g. thegreenyoga.com) Standard sign-up form
    Pop-up form sibforms.com Pop-up form
    Not sure sibforms.com and your-website-domain.com All types

    To learn more about the different ways to share a form, check our dedicated section in the article Create a sign-up form in Brevo.

  6. Click Submit.

Your reCAPTCHA is now created. You will see a page displaying the Site Key and Secret Key. Keep this page open, as you will need these keys for Step 2 to configure the reCAPTCHA within your form.

forms_captcha_secret-key_site-key_en-us.jpeg

Step 2: Add the CAPTCHA to a sign-up form

To add the CAPTCHA to a sign-up form created in Brevo:

  1. Log into your Brevo account.
  2. Go to Marketing > Forms.

  3. Create a new sign-up form or open an existing one.
    ➡️ To learn more, check our dedicated articles Create a sign-up form in Brevo and Create a pop-up sign-up form in Brevo. 

    Standard sign-up form Pop-up form
    1. At the Design step, drag and drop the Captcha block into your sign-up form.
      forms_captcha-block_en-us.jpeg
    2. In the Captcha Type dropdown, select either reCAPTCHA v2, reCAPTCHA v3 or Cloudflare based on the CAPTCHA you created in Step 1.
    3. Copy and paste the Site Key and Secret Key that were displayed after completing Step 1 in their respective fields.
    4. (Optional) Add a Label name and Help text to your CAPTCHA.

    5. If you created a reCAPTCHA v2 with the Invisible reCAPTCHA badge in Step 1, select Invisible Captcha.

      contacts_forms_recaptcha.png

That's it! You've added the CAPTCHA to your sign-up form. Now, complete the setup of your sign-up form and share it on your website.

➡️ To learn more, check our dedicated article Create a sign-up form in Brevo - Share your sign-up form.

Troubleshooting

💡 Good to know
If you are using the Brevo sign-up forms via the WordPress plugin, check our dedicated troubleshooting section in the article Brevo plugin for WordPress - Connect your WordPress site with Brevo.

After setting up your form, open it to check for any error messages. Here are some troubleshooting tips for common CAPTCHA-related errors and issues:

❌ I get the error "Invalid domain for site key"

The domain you have to enter in Google or Cloudflare depends on how you plan to share the form on your website:

  • If you want to share your form using Quick Share or Iframe
    Add the domain sibforms.com. It is the domain Brevo uses to host the form.
  • If you want to integrate your form with HTML
    Add the domain of the website where you will display the form. For instance, if you want to add the form on http://www.thegreenyoga.com, add thegreenyoga.com in this field.
    • 💡 Good to know
    If you are not sure which domain to add, you can add both sibforms.com and your-website-domain.com. This option works for all form sharing methods and prevents the most common CAPTCHA errors.
❌ I get the error "Invalid key type"

When adding a reCAPTCHA to a form, ensure you enter the Site Key and Secret Key specific to the type of reCAPTCHA you created.

➡️  For example
If you created a Google v3 reCaptcha in Step 1, ensure you select reCaptcha v3 in the Captcha Type dropdown in the form editor during Step 2.

Site Keys and Secret Keys for one type are independent of the other type:

  • Keys for Checkbox reCAPTCHA should only be used for Checkbox reCAPTCHA and not for Invisible reCAPTCHA.
  • Keys for Invisible reCAPTCHA should only be used for Invisible reCAPTCHA and not for Checkbox reCAPTCHA.
❌ I can't see the Simple HTML option to share my form

If you include a CAPTCHA, you won't be able to share your form with Simple HTML. Simple HTML is a simplified version of your form's HTML that doesn't need JavaScript. However, since CAPTCHA requires JavaScript, it won't be possible to share your form via Simple HTML.

❌ I used the same Site Key and Secret Key on multiple forms
We do not recommend using the same Site Key and Secret Key on multiple forms as it can sometimes cause errors and conflicts with the forms.

⏩ What's next?

🤔 Have a question?

If you have a question, feel free to contact our support team by creating a ticket from your account. If you don't have an account yet, you can contact us here.

If you’re looking for help with a project using Brevo, we can match you with the right certified Brevo Agency partner.

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