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Pre-filling a campaign form

If you are guiding an existing, known lead to a GymOS campaign form or landing page, you may add additional query string parameters to prefill form fields. This will simplify the sign-up process for the lead and, if they have registered previously, it will also reduce the likelihood of “already registered” errors.

Assembling the URL manually

If you are using an external system to communicate with the lead and guide them into your GymOS campaign, you can build the query string to append to the campaign URL manually.

The query parameters accepted by GymOS are:

  • pn = the name of the lead
  • pe = the email address for the lead
  • pm = the mobile number for the lead

As per standard web rules, all query parameters must be URL encoded and appropriately joined with ? and & operators, as appropriate. Most marketing applications provide functions for URL encoding.

For example, if your campaign URL was https://members.demogym.co.uk/c/l/7HyPo/1TenlD8U/ and you wished to append details for Janine D’Angelo with email address [email protected] and mobile number +44 7803 172829, then you would build your URL as below:

https://members.demogym.co.uk/c/l/7HyPo/1TenlD8U/
   ?pn=Janine%20D%27Angelo
   &pe=janine%40hotmail.com
   &pm=%2B44%207803%20172829

Note: Your final URL would be all one line, and not contain the line breaks and spaces added above for presentation purposes.

Assembling the URL in GymOS

If your lead is already in GymOS you may use the same principles as above, combined with GymOS’ merge fields and encoding options to build the URL for you.

For example, if your campaign URL was https://members.demogym.co.uk/c/l/7HyPo/1TenlD8U/ and you wished to send an email to a lead(s) pointing them to that campaign and pre-filling the form, you would use the structure below:

https://members.demogym.co.uk/c/l/7HyPo/1TenlD8U/
   ?pn=[[LEAD.FIRSTNAME.U]]%20[[LEAD.LASTNAME.U]]
   &pe=[[LEAD.EMAIL.U]]
   &pm=[[LEAD.MOBILE.U]]

Note: Your final URL would be a single line, without the line breaks and spaces added above for presentation purposes. When GymOS sends the communication, it would populate and encode the merge fields, and each recipient would receive their corresponding unique URL, pre-populating the GymOS registration form.

Alphonso Wolfe

Applying encoding to GymOS merge fields

In GymOS, you may suffix a merge field with .U to have GymOS apply URL encoding to the merged value. Similarly, you may suffix a merge field with .H to have GymOS apply HTML encoding to the merged value.
In the above example, the .U suffix is used to URL-encode the merge fields for use in a URL.

Lead Campaign Prefill Field

As of 07/04/2026, a new merge field [[LEAD.CAMPAIGNPREFILL]] is available, which assembles the data suffix (starting from the ‘?’) for you. Thus, you could use the shorthand syntax below to achieve the same as outlined above longhand:

https://members.demogym.co.uk/c/l/7HyPo/1TenlD8U/[[LEAD.CAMPAIGNPREFILL]]
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