The `"mime_types_handler"` manifest key registers your extension as a handler for supported MIME types, such as `application/pdf`. When a user opens a document of a registered MIME type, Chrome loads your handler page in place of its built-in viewer.

For more information and examples, see the [`chrome.mimeHandler`](https://developer.chrome.com/docs/extensions/reference/api/mimeHandler) API documentation.

    {
      // ...
      "mime_types_handler": {
        "application/pdf": {
          "handler_url": "viewer.html",
          "can_embed": true
        }
      },
      // ...
    }

`"mime_types_handler"` (dictionary, optional)
:   Maps MIME types to the extension pages that render them. As of Chrome 151, `application/pdf` is the only MIME type available to public handlers. Declaring an unsupported MIME type causes an installation warning.

`"handler_url"` (string, required)
:   The HTML file to display when a document of the corresponding MIME type is opened. This file must be located within your extension.

`"can_embed"` (boolean, optional)
:   Specifies whether to handle documents embedded in `<embed>`, `<object>`, or `<iframe>` elements. Defaults to `false`, meaning the handler only receives top-level navigations.