Custom Forms: Server Side & Browser Side Recommendations

Marketo Employee
Marketo Employee

With a server side approach, you have a couple of options using the Marketo REST API:


Submit Form API

  • With this approach you’ll still need to create and approve a form in Marketo with the same fields as your custom form but you don’t need to embed it on your page.
  • When a lead fills out and submits your custom form, you’ll need to queue up the submitted data so it can be processed one at a time, with implications on the concurrency limit of the Marketo REST API (Maxiumum 10 concurrent calls).
  • The body of the API call will just be a single array item containing the fields from the form you created in Marketo and the form’s ID.
  • The upside to this approach is that it will generate Marketo Form activities, which you can leverage through Smart List filters and triggers. You’ll also be able to use reporting features without embedding a hidden form on your page.
  • This process will also allow you to capture and associate the cookie to the lead who fills out the form.


Create/Update Lead API

  • This is similar to the Submit Form API approach but won’t require you to create a form in Marketo first. You’ll still need to queue up the data before sending it to Marketo though.
  • The primary upside is that you don’t need to create a form in your Marketo instance but the downside is that you’ll lose the native activities for Form Fillouts and the associated Smart List filters and triggers and reporting as well.
  • This approach is common for customers who leverage an external data warehouse to manage their lead data outside of Marketo.


With the browser side approach, you have a single option that leverage the Marketo JS API:

Marketo Forms 2.0 JS API

  • With this approach, you’ll need to create a form in your Marketo instance but won’t need to add any fields initially.
  • The blank form can then be embed on your page in the background and you can use custom JS to append field values captured by your custom form before submitting it to Marketo.
  • The benefits of this approach are that you won’t need to queue or send the data to a separate DB first and you’ll also be able to leverage Marketo Form Smart List filters, triggers and reporting.


Each of these options has their own pros and cons so it’s really up to you to determine which approach best meets your use case requirements.