Lead tracking: hidden fields & URL parameters

Automatically track your prospects with hidden fields and URL parameters.

Written By CrocoTeam

Last updated 3 days ago

CrocoClick lets you track where your leads come from, without any complex external tools. Using hidden fields in your forms and URL parameters, you can automatically record the source, campaign, or marketing channel associated with each lead.

What is a hidden field?

A hidden field is a form field that is invisible to the visitor but can be automatically filled in if a value is present in the URL.

Simple example

URL: https://monlien.com/optin?source=instagram

Form with a hidden field named "source"

➞ The field will be automatically filled with the value "instagram" without any action required from the user.

💡 TIP: You can pre-fill multiple hidden fields in a single URL.

Complete example:

https://monlien.com/optin?source=insta&email=bob@superdomaine.com&ad_name=story1

Why not just use the native "source" field?

Native source field (CrocoClick)

Custom hidden field

Automatically filled by CrocoClick (first or last known source)

Filled in manually via the URL

Useful for overall statistics

Ideal for tracking a specific campaign

Can be modified if the contact returns via another channel

Does not change once entered

💡 TIP: Use a hidden field like source2 to lock in the exact source from the start, even if the contact navigates elsewhere afterward.

How do I set up a hidden tracking field?

Step 1 — Add the field to the form

  1. Open your form in CrocoClick

  2. Add a hidden field and name it source2 (or according to your convention).

  1. Name it source, source2, or according to your logic (e.g., utm_campaign, canal, ad_name, etc.).

  2. Leave the value blank

Step 2 — Create your URL with the correct parameters

Add the data to be transmitted to the end of your URL:

https://monlien.com/optin?source2=instagram

TIP: No need to modify the URL; simply add ?name=yourdata to the end of the URL before sharing it

Each field in your form with the same name will be filled with the corresponding value.

💡 TIP: To combine multiple pieces of data, use "&" between the parameters:

?source2=partenariat&ad_name=reel3&landing=page_ete

How do you check if it works?

  1. Open your test URL containing the parameters in an incognito window

  2. Fill out the form as a prospect would

  3. Go to Contacts > Contact Details

  4. Check the custom fields:

    source2 = instagram

Best practices

  • Keep names simple and consistent

  • We recommend not replacing the native "source" field, as it serves as a "fallback source" by automatically tracking certain parameters and UTMs

  • Always test your URLs before launching a campaign

Conclusion

Hidden fields + URL parameters allow you to improve the accuracy of your tracking and better understand where your leads are coming from.

It’s a simple yet extremely powerful tool for your future campaigns, analytics, and automations!