--- title: Create or Replace a Thumbnail framework: ClassKit Catalog API role: symbol role_heading: Web Service Endpoint platforms: [classkit 1.0+] path: classkitcatalogapi/create-or-replace-a-thumbnail --- # Create or Replace a Thumbnail Store an image that represents one of your app’s assignable activities. ## URL POST https://classkit-catalog.apple.com/v1/thumbnails ## Query Parameters environment: The development or production environment to use for this access. For details, see Testing Your ClassKit Catalog Implementation. thumbnailId: The thumbnail identifier for the thumbnail to upload. Format this value as a URL-encoded string. ## Response Codes 201 Created: The request succeeded. 202 Accepted: The API accepted, but hasn’t completed the request. To ask for a status update later, see Get Status. 400 Bad Request: The request contained an error. 403 Forbidden: The request wasn’t authorized. ## Discussion Discussion You can associate a thumbnail image with one or more contexts. Create an association by matching the thumbnailId value that you provide as a query parameter to this call with the thumbnailId field of a Context.Data object that you upload with a call to Create or Replace Contexts. Upload the context that references a thumbnail before uploading the thumbnail. Provide the thumbnail image as binary data in the request body. For example, after obtaining a web token, as Authenticating Calls to the ClassKit Catalog API describes, you could use the following curl command to upload the image in the file catalog.png: % curl --request POST \ --url 'https://classkit-catalog.apple.com/v1/thumbnails?thumbnailId=catalog.png&environment=production' \ --header 'authorization: Bearer ' \ --header 'content-type: image/png' \ --data-binary '@catalog.png' Follow the same guidelines for creating thumbnails as you follow when working with the ClassKit API in your app. In particular, provide images that are at least 80 x 80 pixels, and no larger than 330 x 330 pixels. The system ignores thumbnails that are too small, and scales down thumbnails that are too large. Use a thumbnail with the maximum dimensions to produce the best result across devices. If you delete every context that references a thumbnail, the system automatically deletes the thumbnail image as well. ## See Also ### Uploading Thumbnails - [Get a Thumbnail](classkitcatalogapi/get-a-thumbnail.md) - [Delete a Thumbnail](classkitcatalogapi/delete-a-thumbnail.md)