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Documentation Index

Fetch the complete documentation index at: https://filla.io/docs/llms.txt

Use this file to discover all available pages before exploring further.

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What URL prefilling does

You can pass field values as query parameters in your form URL. When the form loads, those values are automatically filled into the corresponding fields. Respondents can still change the values unless the fields are set to read-only. This is useful for:
  • Personalizing forms sent to known contacts (pre-fill their name and email)
  • Tracking which campaign or source a respondent came from
  • Pre-selecting a product, plan, or option based on where the respondent came from
  • Passing internal IDs from your system into the form

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URL format

Add query parameters to your form URL using the prefill_ prefix followed by the Airtable field name (exactly as it appears in your base): 
https://app.filla.io/forms/{formId}?prefill_Name=Jane+Smith&prefill_Email=jane@example.com
Filla reads the prefill_* parameters from the URL, strips the prefill_ prefix, and looks up a field in the connected table whose name matches the remainder. The matched fields are pre-populated when the form loads.
Only field names work, not field IDs. prefill_fldXXXXXXXXXXXXXX=value will be silently ignored. Always use the human-readable field name from your Airtable table — for example prefill_Email, not prefill_fldAbc123Xyz. If your field name contains spaces, URL-encode them (prefill_Full+Name=Jane).

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Pre-fill tab in the Share view

The Pre-fill tab in the Share view (accessible from the Share tab in the form editor) provides a ready-to-use Airtable formula for generating per-record edit links: 
"<formUrl>/" & RECORD_ID()
This formula creates a unique URL for each record in your Airtable table. Paste it into a formula field in Airtable to generate edit links for every record. Click the Copy formula button to copy the formula to your clipboard.

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Supported field types for prefilling

Field typeNotes
Single line textValue used as-is
Multiline textValue used as-is
EmailValue used as-is
URLValue used as-is
Number / Currency / PercentPass a numeric value
Single selectPass the exact option name (case-sensitive)
DatePass in YYYY-MM-DD format
CheckboxPass true or false
Linked recordPass the Airtable record ID (starts with rec)

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Example

Pre-fill a contact form with a name and email from a CRM link: 
https://app.filla.io/forms/frmXyz?prefill_Name=Jane+Smith&prefill_Email=jane@example.com
The respondent opens the form and sees their name and email already filled in.

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Prefilling read-only fields

By default, respondents can change pre-filled values. If you want to lock a value so the respondent cannot edit it (for example, an internal tracking ID, a plan tier, or a referral source):
  1. Open the field in the form editor
  2. In the right-side panel, enable Read-only
  3. Share the form with the value in the URL: ?prefill_<FieldName>=value
That’s it. A read-only field picks up its value from the URL parameter directly — no special syntax, no default value configuration required. The URL prefill writes into the field, the read-only toggle prevents the respondent from changing it.
You do not need to set a Default value of {{prefill_FieldName}} or similar — that syntax doesn’t exist. URL parameters are already read straight into the field. Default values are a separate mechanism for filling fields when no URL parameter is present (see Default values and prefilling).

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Auto-stamping today’s date (no URL required)

For Date and Date Time fields, you don’t need a URL parameter to lock in today’s date. Enable Auto-fill today’s date on the field, then enable Read-only — the field stamps the current date automatically the moment the form loads, and the respondent can’t change it. See Date fields for the full pattern.

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Conflict with default values

If both a URL parameter and a field’s Default value setting are provided for the same field, the URL parameter takes precedence.

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Common questions

Yes. Query parameters are visible in the browser address bar. Do not pass sensitive data (passwords, private tokens) via URL parameters.
If the value doesn’t match an existing option, the field stays empty. The value must exactly match an existing option name.
No. Prefill only works with field names — prefill_fldAbc123=value will be ignored. Use the field name as it appears in Airtable, e.g. prefill_Email=jane@example.com. This is intentional: field names are stable per-form and readable in the URL, and field IDs change if you duplicate a base.
Yes. Append the query parameters to the form URL when building your embed code’s src attribute.
Use standard URL encoding. Spaces can be written as + or %20. Other special characters should be percent-encoded (@ = %40, # = %23, etc.).
No. URL parameters are read directly into the field — you don’t need to set a Default value like {{prefill_FieldName}} to make it work (that syntax isn’t supported). Just share a link containing ?prefill_FieldName=value and the field will be populated. Default values are only used when no URL parameter is present.
Yes. Enable Read-only on the field in the form editor, then pass the value via ?prefill_FieldName=value. The respondent sees the value but can’t edit it.