Overriding Chrome settings

Settings overrides are a way for extensions to override selected Chrome settings. The API is available on Windows and Mac in all current versions of Chrome.

Homepage, search provider, and startup pages

Here is an example of how homepage, search provider, and startup pages can be modified in the extension manifest. Any domain used in the settings API must be verified (via Google Search Console) by the same developer account publishing the extension. Note that if you verify ownership for a domain (for example, https://example.com) you can use any subdomain or page (for example, https://app.example.com or https://example.com/page.html) within your extension.

Using the settings override permission while also requesting any additional capabilities or permissions is inconsistent with our single purpose policy. When Chrome detects that an item is potentially violating our single purpose policy, a confirmation dialog is shown to the user. Extensions that limit themselves to only modifying a single setting without seeking additional capabilities or permissions do not get a confirmation dialog.

This applies to Chrome 107 and later.

{
  "name": "My extension",
  ...
  "chrome_settings_overrides": {
    "homepage": "https://www.homepage.com",
    "search_provider": {
        "name": "name.__MSG_url_domain__",
        "keyword": "keyword.__MSG_url_domain__",
        "search_url": "https://www.foo.__MSG_url_domain__/s?q={searchTerms}",
        "favicon_url": "https://www.foo.__MSG_url_domain__/favicon.ico",
        "suggest_url": "https://www.foo.__MSG_url_domain__/suggest?q={searchTerms}",
        "instant_url": "https://www.foo.__MSG_url_domain__/instant?q={searchTerms}",
        "image_url": "https://www.foo.__MSG_url_domain__/image?q={searchTerms}",
        "search_url_post_params": "search_lang=__MSG_url_domain__",
        "suggest_url_post_params": "suggest_lang=__MSG_url_domain__",
        "instant_url_post_params": "instant_lang=__MSG_url_domain__",
        "image_url_post_params": "image_lang=__MSG_url_domain__",
        "alternate_urls": [
          "https://www.moo.__MSG_url_domain__/s?q={searchTerms}",
          "https://www.noo.__MSG_url_domain__/s?q={searchTerms}"
        ],
        "encoding": "UTF-8",
        "is_default": true
    },
    "startup_pages": ["https://www.startup.com"]
   },
   "default_locale": "de",
   ...
}

Customizing values

Values in the manifest can be customized in the following ways:

All values of the search_provider, homepage, and startup_pages properties can be localized using the chrome.i18n API.
For external extensions, the search_provider, homepage and startup_pages URL values can be parametrized using a registry key. Create a new registry entry next to the "update_url" key (see instructions here). The key name is "install_parameter", the value is an arbitrary string:
```
{
  "update_url": "https://clients2.google.com/service/update2/crx",
  "install_parameter": "Value"
}
```
All occurrences of the substring "__PARAM__" in the manifest URLs will be substituted with the "install_parameter" value. If "install_parameter" is absent, occurrences of "__PARAM__" are removed. Note that "__PARAM__" cannot be part of the hostname. It needs to occur after the first '/' in the URL.

Reference

An extension can override one or more of the following properties in the manifest:

alternate_urls (array of strings, optional): A list of URL patterns that can be used in addition to search_url.
encoding (string, optional): The encoding used for search terms. This is required if you don't set prepopulated_id.
favicon_url (string, optional): An icon URL for the search engine. This is required if you don't set prepopulated_id.
homepage (string, optional): The new value for the homepage.
image_url (string, optional): The URL the search engine uses for image search. If this isn't used, the engine doesn't support image search.
image_url_post_params (string, optional): The post parameters for image_url.
is_default (boolean, required): Specifies whether the search provider should be default.
keyword (string, optional): An omnibox keyword for the search engine. This is required if you don't set prepopulated_id.
name (string, optional): Name of the search engine displayed to user. This is required if you don't set prepopulated_id.
prepopulated_id (integer, optional): An ID for Chrome's built-in search engine.
search_provider (object, optional): A search engine.
search_url (string, required): The search URL the search engine uses.
search_url_post_params (string, optional): The post parameters for search_url.
startup_pages (array of strings, optional): An array of length one containing a URL to be used as the startup page.
suggest_url (string, optional): The URL the search engine uses for suggestions. If this isn't used, the engine doesn't support suggestions.
suggest_url_post_params (string, optional): The post parameters for suggest_url.