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+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 <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/newtab/data/content/tippytop <browser/components/newtab/data/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 <browser/components/search/extensions>`.
+  * 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 <browser/installer/allowed-dupes.mn>`
+    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 <browser/components/newtab/data/content/tippytop>`.