# Application Search Engines Firefox defines various application search engines that are shipped to users. The extensions for the definitions of these engines live in {searchfox}`browser/components/search/extensions ` ## Icons ### Icon Requirements It is preferred that each engine is shipped with a `.ico` file with two sizes of image contained within the file: - 16 x 16 pixels - 32 x 32 pixels Some engines also have icons in {searchfox}`browser/components/topsites/content/tippytop `. For these engines, there are two sizes depending on the subdirectory: - `favicons/`: 32 x 32 pixels - `images/`: preferred minimum of 192 x 192 pixels ### Updating Icons To update icons for application search engines: - Place the new icon file in the {searchfox}`folder associated with the search engine `. - Increase the version number in the associated manifest file. This ensures that the add-on manager properly updates the engine. - Be aware that the {searchfox}`allowed-dupes.mn file ` lists some icons that are intended as duplicates. To update icons for tippytop: - Place the new icon file in {searchfox}`both the sub-folders within the tippytop directory `.