Hidden fields and prefilled values
A hidden field carries a value the person filling in the form never sees. It travels with their answer, so a response can arrive already marked with the newsletter that sent them, the branch the link belongs to, or a reference number you need to match it against later.
The same panel holds the other half of this. A default value prefills a field people can see, so a form opens part-filled instead of blank. Both are set on the Fields tab, one field at a time.
Add a Hidden field
Hidden sits in the Layout section of the field palette, down the left of the Fields tab, under Essentials, Input, Choice and Upload. Adding one drops a grey line reading "Hidden: Hidden field" into your document. Nothing renders on the published form — no label, no box, no gap where it would have been.
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Open the form, stay on the Fields tab, and expand Layout in the palette on the left.
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Click Hidden. The field lands at the end of the document and the Field Properties panel opens on the right.
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Replace the Label. It doubles as the key you fill the field by, so keep it short and URL-safe: source, campaign, ref.
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Type a fallback into Default value — website, say — then click away from the box. Edits here save as you make them; the Fields tab has no Save button.
Default value holds up to 255 characters. Because the label becomes the URL key, spaces in the label mean %20 in the link — rename the field before you share anything.
Fill it from the link
On the hosted form, a hidden field reads its value from the query string of the address that opened the page. The parameter name has to match the field's label exactly — character for character, capitals included.
A volunteer sign-up form with a field labelled source tells two audiences apart on its own. Mail the list .../f/aB3xY9/volunteer-signup?source=newsletter, print ?source=poster on the flyer, and every response says where it came from. Take the base link from the Share button in the editor header and add the parameter yourself.
A missing or misspelled parameter is ignored without complaint and the field falls back to Default value. That fallback is the reason to set one — a response marked website reads better than an empty cell.
Prefill a field people can see
Default value is not only for hidden fields. Short Text, Long Text, Email, Number, Phone and Date each have the same box in Field Properties, and whatever you put there sits in the field when the form loads, ready to be typed over. A weekly restock form that always goes to one depot can open with the depot already filled in.
Dropdown, Radio and Checkbox have no Default value box, so an option cannot be preselected.
Visible fields take their default from the editor and nowhere else. The query-string trick applies to Hidden fields only — ?Email=someone@example.com will not fill an email field.
Where the values turn up
After the submit, a hidden field behaves like any other answer: a column in the table on the Submissions tab, a line of its own on the individual response page, a column in the file from Export CSV, and a key named after its label in the payload sent to webhooks and to Zapier.
On an encrypted form the hidden value is sealed with the rest of the response and reads as ciphertext until your browser decrypts it with your private key. Lose that key and the responses cannot be recovered by anyone, us included.
What a hidden field will not do
It is hidden from view, not secret. The value sits in the page source and anyone can edit the link before they submit, so treat it as a label on the response rather than something you trust. Internal prices and tokens stay out of it.
Hidden fields also cannot drive conditional logic. The field list inside Edit Logic offers only fields the visitor answers, so a question cannot be made to appear because ?source=newsletter was in the link.
The embed script builds the form inside your own page and reads only Default value; parameters on the surrounding page never reach it. To pass a value into an embedded form, use the iframe snippet from the Share dialog and put the parameter on its src.
Frequently asked questions
Can I capture utm_source and the rest of the UTM tags?
Yes — one hidden field per parameter, labelled exactly utm_source, utm_medium, utm_campaign. Only the tags on the form's own address are read. If someone lands on your site with UTM tags and then clicks through, those tags are gone by the time the form loads, so carry them on the link you share.
My hidden field is empty in the export — what went wrong?
Almost always the parameter name and the field label do not match. Source and source are different keys, and a trailing space in the label counts. Open your test link, view the page source, and check the hidden input holds what you expect before sending the link out.
Does it matter where in the form the hidden field sits?
Not on an ordinary form — it renders nothing, so its position changes nothing. On a form with page breaks it does: a hidden field sitting alone between two breaks still counts as a page, and the respondent gets an empty step to click through. Keep it on a page with real questions on it.
Related articles
- How the form editor works
The editor has three parts — palette, form, field settings — and edits to fields save as you make them.
- Every field type, and when to use it
A tour of the palette: what each field type collects, and which one fits the answer you want back.
- Show and hide fields with conditional logic
Add a rule to a field so it appears, or becomes required, only when an earlier answer calls for it.
- Share a form by link
Every form has a public link from the day it is created — here is where to find it and how to send it.
- Required fields and validation
Turn on Required, set length, number and date limits, and require a field only when an earlier answer calls for it.
Nothing here answering your question? The editor is quick enough that trying it is often faster than reading about it.
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