The preference browser.urlbar.default.behavior makes it possible to customize the search behavior of the location bar in Firefox 3.5 and SeaMonkey 2. It replaces browser.urlbar.matchOnlyTyped, which is no longer supported.
The decimal value of this preference should be seen as a bitmap of 6 bits. If a bit in that bitmap is 1 then the corresponding filter will be applied. There are restrict filters (0:History, 1:Bookmarks, 2:Tags, 5:Typed) and match filters (3:Title, 4:URL).
Quote from "defaults\prefs\firefox.js" : "The default behavior for the urlbar can be configured to use any combination of the restrict or match filters with each additional filter restricting more (intersection)."
You can override the default filter by using commands in the location bar. See Location Bar search.
See the articles below by Edward Lee (edilee) for more information and tips.
The default of this preference in Firefox 3.5 and above is 0, meaning that no filtering is applied. 
The default of this preference in SeaMonkey 2 is 1, meaning that only History items are shown. 
Possible values and their effects
The section shows the meaning of the 6 bits (0-5) that are currently used to compose the default filter for the location bar.
Add up the following values to set the behavior as the default (i.e., 17=History+match URL; 49=History+match URL+Typed).
Note: In SeaMonkey 2.0, only autocomplete entries for visited pages (History) are generated so setting the value to 2 (Restrict: Bookmarks) or 4 (Restrict: Tags) will not produce any results. In SeaMonkey 2.1 and later, all options are supported and produce the expected results, including the value 0.
Restrict: History (^)
Restrict: Bookmarks (*)
Restrict: Tags (+)
Match: Title (#)
Match: URL (@)
Restrict: Typed (~)
Restrict: Open Tabs (Switch to tab) (%)
Tools -> Options -> Privacy -> Location Bar
- Nothing (browser.urlbar.autocomplete.enabled=false; browser.urlbar.default.behavior unchanged)
- History and Bookmarks (0)
- History (1)
- Bookmarks (2)
Other match and restrict bits that are set remain unaffected.
Edit -> Preferences -> Browser -> Location Bar
- "Match only websites you've typed previously": 33 (1+32)
- "Only match locations, not website titles": 17 (1+16)
If both options are checked, the preference value becomes 49 (1+16+32).
First checked in
Has an effect in
- Firefox 3.5 (nightly builds since 2008-12-17)
- The value 32 only works in builds since 2009-01-07
- Values 64 and 128 only work in Firefox 4 and later
- SeaMonkey 2 (nightly builds since 2009-01-10)
- Bug 463459 - Use a separate pref instead of empty restrict/match values to specify defaults
- Bug 463483 - matchOnlyTyped no longer honored with special filters
- Bug 463558 - Switch matchOnlyTyped to restrict.typed "~" (default.behavior + 32)
- Bug 472943 - Two confusable preferences, "browser.urlbar.search.sources" and "browser.urlbar.default.behavior", should be unified
- Bug 468326 - Add UI prefs for new places history functionality (SeaMonkey)
- Bug 470031 - use new browser.urlbar.default.behavior pref for restricting places searches (SeaMonkey)