Responder UUIDs

Identifying individual responders using a unique ID.

A responder UUID (Universally Unique Identifier) is a unique value used to identify a user's browser session. This UUID is automatically generated by Formsort when a user loads a form for the first time and is stored in their browser’s localStorage.

By default, the UUID persists across visits, allowing Formsort to:

• Recognize returning users,

• Restore saved answers,

• And tie together session-specific data like events and submissions.

When Is a Responder UUID Generated?

You don’t need to provide a UUID manually. Formsort automatically generates a responderUuid during a responder’s first session.

If you’d like to generate a new UUID every time someone visits your form (even in the same browser), enable Start each session as a new responder in your variant settings.

Manually Setting a Responder UUID

While auto-generation works for most use cases, you can also provide your own responder UUID. This is useful if:

• You already have a unique identifier for a user (e.g. a user ID or session ID),

• You want to force-load a specific session tied to that identifier.

Two ways to set the responder UUID manually:

1. Via the URL parameter responderUuid:

https://<FLOW-URL>?responderUuid=123e4567-e89b-12d3-a456-426614174000

1. Via HTML POST body:

<input name="responderUuid" value="123e4567-e89b-12d3-a456-426614174000" />

💡You can also use URL parameters to set initial answers in the form—see our full guide for more.

Important notes:

• responderUuid must be a valid UUID string in the format: xxxxxxxx-xxxx-xxxx-xxxx-xxxxxxxxxxxx (e.g., 123e4567-e89b-12d3-a456-426614174000)

• Force-loading a session with responderUuid will not work if:

  • Start each session as a new responder is enabled, or

  • The user’s previous session has been finalized.

Making the responder UUID available as an answer

You can make the responderUuid available as an answer variable in your flow by adding it from the System Library into your form schema.

The System Library menu

Once added:

• It can be templated into redirects or API calls, or anywhere templating is allowed.

• You can reference it like any other variable in your flow.

Learn more about variable templating for dynamic usage of answer data in your form logic.