Guides

Hidden fields and prefilled links

Pass values into a form through its link. Keep things you already know, like an email or a plan, with each response, and fill in answers before people start.

Hidden fields

A hidden field saves a value from the link with each response. People filling in the form never see it.

Add the field
In the builder, click the form's name, choose Settings, and find Hidden fields under General. Add a name such as email. Names use letters, numbers, _, - and ., up to 64 characters.
Put the value in the link
Add the name and its value to the form's link, the way you'd add any URL parameter.
Form link
```
https://enform.co/submit/your-form?email=ada@example.com&plan=pro
```
Read it with the response
The value lands in the response's hidden map, by name, in the API, webhooks and Make.
Part of a response
```
{
  "hidden": {
    "email": "ada@example.com",
    "plan": "pro"
  }
}
```

Sending the link from an email tool? Most let you drop in a merge tag, such as ?email={{ email }}, so each person gets their own value.

Prefill answers

You can also fill in a visible question ahead of time. Use the question's ID as the parameter name. Get IDs from GET /forms/{formId}: each question's key is its ID.

Prefilled link

https://enform.co/submit/your-form?bba1826f-56fc-4e44-a0fa-bac06310da49=Ada

For a choice question, pass the option's label or value. Case doesn't matter. Options that don't match are skipped.
For a question that takes several choices, separate them with commas: ?<questionId>=Red,Blue.
File uploads, signatures, grids, rankings, payments and text-only screens can't be prefilled.

Rules for link values

Namescase-insensitive: ?Email= and ?email= fill the same field.
Valuesup to 1,000 characters: Longer values are cut. Blank values are ignored.
Countup to 50: Enform reads the first 50 parameters in a link.
Reservednames: embed, header, preview, snapshot, shell and v are used by Enform, so don't name a hidden field any of these.

Where the values show up

In the REST API and webhooks, under hidden by name and under answers by the field's ID.
On your own site, the embed snippet passes them from your page's address to the form.

Hidden fields

Prefill answers

Rules for link values

Where the values show up

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