Search Engines

This document describes the three main ways Firefox serves search engines to the user, enabling users to search the internet with different search providers. The three main ways Firefox serves search engines to the users is through:

  • Add-on Search Engines

  • OpenSearch Engines

  • Enterprise Policy Engines

An example of a search provider is Google, which is one of the Add-on Search Engines described in the first section below. Another example of a search provider is Bugzilla, which is an OpenSearch Engine described in the second section below. Lastly, there are Enterprise Policy Search Engines, which will be the third section described in this documentation.

Add-on Search Engines

Add-ons are additional functionality that third-party developers provide for users to install into Firefox. The add-on mechanism is also used by Firefox to ship the search engines provided by the application. To define Add-on Search Engines, developers use the WebExtensions API. Since the WebExtensions API technology is used, developers interchangeably used the term WebExtension Search Engines when referring to Add-ons Search Engines.

The list of Add-on Search Engines provided by Firefox and their extension files can be found in mozilla-central/browser/components/search/extensions. Within each Add-on Search Engine folder, there is a manifest.json file. One of the keys in that manifest.json file is chrome_settings_overrides, whose value is an object that describes how to construct the url, images, strings, icon, etc. Here’s an example of how the search provider is set within chrome_settings_overrides:

"chrome_settings_overrides": {
  "search_provider": {
  "name": "Discogs",
  "search_url": "{searchTerms}",
  "keyword": "disc",
  "favicon_url": ""

To see more details on the syntax and properties, visit the chrome settings overrides MDN documentation.

In Practice

All versions of Firefox support add-ons. Firefox switched over from OpenSearch to Add-on Search Engines internally in Firefox version 78. Add-on Search engines allows Firefox developers to have more flexibility and control in the modification of formatting search engines as we support different search providers.

We maintain these Add-on Search Engines through a search configuration file that is bundled and configured via Remote Settings. As of this writing, June 2022, we use Remote Settings for managing search engines only for Firefox Desktop but not outside of Firefox Desktop.

OpenSearch Engines

OpenSearch is a plugin, software installed on Firefox to enhance capabilities for searching. OpenSearch has a collection of formats that describe how to construct the url, images, strings, icon, etc. These formats provided by OpenSearch allow Firefox to make a search over the internet with a specific search provider that is not an application provided search engine on Firefox. The purpose of OpenSearch is to provide more convenient ways of searching and different ways of searching.

OpenSearch allows users to search with a vast variety of search providers which do not come installed with Firefox out of the box. The main benefit of OpenSearch is it allows site owners to easily provide users with a way to search a site.


Prior to OpenSearch, search plugins were first created by the Mycroft Project and based off of Sherlock, a file and web search tool created by Apple.

The OpenSearch Protocol was created and launched by in 2005. OpenSearch was added to Firefox version 2 in the year 2006. As of today in 2022, OpenSearch is a collection of formats for sharing of search results. The code is stable but unchanged for many years.

See the OpenSearch Documentation for more information on the OpenSearch formats.


Autodiscovery is a feature on Firefox which automatically notifies the user when the webpage they visited has a search plugin.

Here is an example of Autodiscovery from Bugzilla. You can visit and Firefox will automatically detect that the website has a provided search plugin. In the results dropdown, you can look at the search engine shortcuts section at the bottom and it will show a green plus sign over the Bugzilla search icon. The green plus sign indicates that the user can add Bugzilla as an OpenSearch Engine. After the user adds Bugzilla as an OpenSearch Engine, the green plus icon disappears. The user can now click the Bugzilla icon to make a search directly on

Image of the address bar input showing a URL
Image of the address bar input showing a URL

See the Autodiscovery MDN Documentation for more information on Autodiscovery.

Enterprise Policy Engines

Enterprise Policies are customizable configurations for the Firefox browser set by enterprises or companies who want to distribute configuration for their users. The idea of Enterprise Policies is to allow companies to customize Firefox and how their users can or cannot change the usage of Firefox based on predefined configuration that was set in place.

Enterprise Policy Engines are search engines that a company has added as search engines on Firefox for their users by setting the Enterprise Policy. In this Enterprise Policy Documentation, it outlines the different options that are available for enterprises using Firefox ESR (Extended Support Release) and what’s available in terms of adding, updating, or removing search engines. The company can use the policy to define which search engines are available on their Firefox ESR.

See the policy-templates for more information on Enterprise Policy templates and the different configuration rules available.


In practice, there are different ways for a company to specify their policy, depending on which operating system their machines are on. The admin can configure the policy on a server and when the user logs in, those configurations are automatically pushed to the user’s Firefox.

For Windows, the GPO (Group Policy Object) or Intune (Microsoft Endpoint Manager) is used to set the policy. For macOS, configuration profiles are created. For the generic case, there is a JSON file to describe the policy.

When these configurations are set, Firefox takes the configuration as inputs and turns them into settings that Firefox can consume.

A Hypothetical Use of Enterprise Policy

A company that is in the banking industry and requires tighter security over their users may not want their users to do something on Firefox without the company’s knowledge. It may make sense for the company to disable private browsing for Firefox.

Within a specific company, the employees of the finance department could use the Firefox ESR version. In this situation, we think of the finance department as the Firefox user rather than the individual employees as Firefox users. The department makes choices for the individuals that use the Firefox browser through the Enterprise Policy.

Features On Enterprise Policy

All Firefox versions have to honor the Enterprise Policy, but the Enterprise Policy may not have effect on an individual who is not using Firefox ESR at a company. There are features that are enterprise specific that are only available in ESR. These features allow search engines to be configured, allowing for unsigned extensions, installing search engines, and setting a default search engine.

How To Set Up and Use an Enterprise Policy for Firefox

Install the ESR version of Firefox since Enterprise Policies are not supported on rapid release. Then, create the JSON file that is located in the within There are instructions there on how to configure and use the policy. Once the JSON is created with the appropriate settings, drop the JSON file in the directory outlined by the and Firefox will find it and Firefox will open and run with the policy.

Common formatting mistakes are often made when creating the JSON file. The JSON file can be validated using a JSON validator such as