Advanced Configuration

You can pre-fill supported questions by adding response_ query parameters to a generated feedback link. Use this when you already know part of a respondent's answer, want to create personalized links, or want a one-click response from an email or campaign.

For example, this link pre-fills an email question whose slug is email and an NPS question whose slug is nps:

https://form.encatch.com/<shareable-link-id>?response_email=user%40example.com&response_nps=9

Prefilling changes the initial values shown in the form. It does not submit the form; the respondent can review or change the answers before submitting.

Parameter format

Use one of these formats:

response_<question-id-or-slug>=<value>
response_<question-id-or-slug>[<member>]=<value>

• Start every response parameter with the exact, case-sensitive prefix response_.
• Identify a question using its UUID or a unique question slug. An exact UUID match takes precedence. A duplicated or unknown slug is ignored.
• Supply the raw answer value, not an answer object or JSON document.
• Use repeated parameters for multi-value answers. A comma is treated as part of one value, not as a separator.
• Use bracketed member keys for matrix rows and address fields.
• Apply normal URL percent encoding. No additional JSON, Base64, or custom encoding layer is required.

When generating links in JavaScript, URL and URLSearchParams handle encoding safely:

const link = new URL('https://form.encatch.com/<shareable-link-id>');

link.searchParams.set('response_email', 'user@example.com');
link.searchParams.set('response_nps', '9');
link.searchParams.append('response_features', 'analytics');
link.searchParams.append('response_features', 'exports');

console.log(link.toString());

Scalar questions

Scalar questions accept exactly one non-empty value per question.

For choice questions, use the option's stored ID or Value, not its visible label. Prefilling an Other option is not supported.

Multi-value and ordered questions

Repeat the same parameter once for every selection:

?response_features=analytics&response_features=exports

Ranking example:

?response_priority=quality&response_priority=speed&response_priority=price

Nested-selection example:

?response_location=india&response_location=karnataka&response_location=bengaluru

Use an option ID or value for each entry. Duplicate values, unknown options, incomplete nested paths, and values beyond configured selection limits are ignored for that question.

Matrix questions

Use the matrix row ID or value inside brackets. Use a selectable option ID or value on the right side.

Single-choice matrix:

?response_service[mobile]=good&response_service[desktop]=excellent

Multiple-choice matrix—repeat the same bracketed row key:

?response_service[mobile]=fast&response_service[mobile]=accessible

Rating matrix:

?response_satisfaction[reliability]=scale-very-satisfied-id

When constructing the URL manually, brackets may be percent-encoded as %5B and %5D. For example, response_service%5Bmobile%5D is equivalent to response_service[mobile].

For the most reliable result, use row, column, and scale-point IDs from the form configuration. Multiple-choice matrix limits are validated per row.

Address questions

Use bracketed address field names. You may pre-fill one or more enabled fields:

?response_shipping[city]=Bengaluru&response_shipping[country]=IN

Supported member names are:

• addressLine1
• addressLine2
• city
• stateProvince
• postalCode
• country

Disabled address fields and unknown member names are ignored.

Unsupported question types

URL prefilling is intentionally unavailable for:

• Consent
• Signature
• File upload
• Video, audio, or photo
• Scheduler
• Q&A with AI

Display-only elements such as welcome screens, thank-you screens, message panels, and exit forms cannot have responses.

Validation and invalid values

Each parameter is validated against the published form configuration. An invalid parameter is ignored independently and does not prevent the form from opening or other valid answers from being populated.

Common reasons a value is ignored include:

• The question ID or slug does not exist, or the slug is not unique
• A scalar question appears more than once
• The value is empty or outside the question's configured range
• A choice, row, column, or nested path does not exist
• A bracketed key is malformed or used with the wrong question type
• A question type does not support URL prefilling

Persistence and partial responses

The effective set of valid prefilled responses and context values from en_ctx and context_ define the retained-draft scope:

• Opening the same link parameters restores its saved draft.
• Changing a valid response_, context_, or en_ctx value creates a separate retained-draft scope.
• A restored draft takes precedence for questions it already contains; URL values provide defaults for questions not present in that draft.

If partial responses are enabled, merely opening a prefilled link does not trigger a partial-response API request. A partial response becomes eligible only after the effective answer state differs from the initialized state. Final form submission is unchanged.

The response_, context_, and en_ctx parameters are excluded from source tracking. Other URL parameters continue to follow the form's Source Tracking configuration.

Pass context variables

Use context_ query parameters when a form's question or section text contains context variables such as {{ context.customer_name }}. Context values personalize the form but do not create responses or identify the respondent.

Use an untyped parameter for a string, or add a bracketed type when the value must be a boolean or number:

context_<variable-name>=<string-value>
context_<variable-name>[string]=<string-value>
context_<variable-name>[boolean]=true|false
context_<variable-name>[number]=<number-value>

For example:

https://form.encatch.com/<shareable-link-id>?context_customer_name=Ada&context_is_trial[boolean]=true&context_invoice_total[number]=1499.50

The form can reference these values as:

Hello {{ context.customer_name }}

Context rules

• The context_ prefix and bracketed type names are case-sensitive.
• Omitting the bracketed type always produces a string. Use this for identifiers with leading zeroes.
• Boolean values accept true or false, ignoring surrounding whitespace and letter case.
• Number values must be finite JSON-style numbers. Values such as 01, NaN, and Infinity are ignored; use a string when formatting must be preserved.
• Variable names may contain letters, numbers, underscores, periods, and hyphens, and may be up to 100 characters long.
• A link may supply up to 50 valid context variables, with up to 10,000 decoded UTF-8 bytes per value.
• The variable names __proto__, constructor, and prototype are not allowed.
• Provide each logical variable only once. Repeating a variable, including with different type annotations, causes that variable to be ignored.
• Brackets may be written literally or percent-encoded as %5B and %5D.
• Invalid context parameters are ignored independently, so other valid context values still apply.

You can combine response and context parameters in the same link:

https://form.encatch.com/<shareable-link-id>?context_customer_name=Ada&context_is_trial[boolean]=true&response_nps=9

When both en_ctx and context_ provide the same top-level variable, a valid context_ value takes precedence. An invalid context_ value is ignored and does not replace the value from en_ctx.

Valid context values are included in the retained-draft scope. Changing a valid context_ value creates a separate retained draft, just like changing a valid prefilled response or en_ctx.

The shareable page removes context_ parameters from the visible address after reading them and retains them across refreshes in its encoded launch parameter. This reduces casual editing but is not tamper protection or encryption. The original link and its values may still be visible to systems through which it is shared.

The context_ parameters are excluded from source tracking. Arbitrary campaign and tracking parameters remain available to the form's Source Tracking configuration.

Related

• Feedback Links
• User Identification
• Source Tracking
• Partial Save