> ## Documentation Index > Fetch the complete documentation index at: https://docs.snagsolutions.io/llms.txt > Use this file to discover all available pages before exploring further. # Custom user attributes > Define custom profile fields, let users edit them, fetch them from the Users API, and save updates. You can add custom fields to user profiles and use them across your website and APIs. Custom attributes are ideal for capturing structured data like "Favorite Team" or "External Profile Link" that isn't part of the default profile. ## Where custom attributes come from * You can define attributes in Admin → Customization → User Profiles. * Or you can create them via API. If you're using the Admin UI, add a new field in the User Profiles section. To use the API, create attributes with a label that users will see. * API: See [Create a new website user attribute](/api-reference/identity/create-a-new-website-user-attribute). You should see the new attribute in Admin → Customization → User Profiles. You must include a valid `X-API-KEY`. Missing or invalid keys result in 403 Forbidden. In Snag's template, custom attributes appear as editable fields in the Edit Profile modal automatically. No extra code is required after you create the attributes. Field order and labels come from how you configured attributes in Admin or via the API. Use the Users API to retrieve users and their saved values for any defined attributes. * API: See [Get users](/api-reference/identity/get-users). Confirm the response includes each user and their stored values for the attributes you defined. When a user edits their profile (or when you set values server-side), upsert attribute values using the attribute values endpoint. * API: See [Create a new website user attribute value](/api-reference/identity/create-a-new-website-user-attribute-value). Re-fetch the user and verify the updated value appears. * **Cause**: Missing or invalid `X-API-KEY`, or insufficient permissions. * **Fix**: Provide a valid API key with permission to write attributes/values for the given `websiteId` and `organizationId`. * **Cause**: Missing required fields (`websiteId`, `organizationId`, `data`), or invalid IDs. - **Fix**: Ensure all IDs are valid UUIDs and the `data` array has the correct shape. * **Cause**: Value upsert succeeded, but UI cache not refreshed. * **Fix**: Re-fetch the user or invalidate client cache after saving. ## Related APIs * [Create a new website user attribute — see API reference](/api-reference/identity/create-a-new-website-user-attribute). * [Get users — see API reference](/api-reference/identity/get-users). * [Create a new website user attribute value — see API reference](/api-reference/identity/create-a-new-website-user-attribute-value). Use consistent labels and avoid storing secrets or sensitive PII in custom attributes.