Tips

URL bar

Prefix search with # search the title of webpages
Prefix search with @ search the url of webpages
Prefix search with % search only open tabs
Prefix search with * search only bookmarked pages
Prefix search with + search only tagged pages
Prefix search with ^ search in browser history
Prefix search with ~ show only results that have been typed
<Shift><Del> on OSX (just <Del> on others) on a result delete it from autocomplete

Default search engine when hitting <Enter> with keywords keyword.URL;https://duckduckgo.com/?q=
Don’t kill http:// in the address bar (defaults to true) browser.urlbar.trimURLs;false
Double click select the whole url (defaults to false) browser.urlbar.doubleClickSelectsAll;true
Make javascript: prefixed url appear in history (defaults to true = exclude them) browser.urlbar.filter.javascript;false

Tabs below address bar (defaults to true = above) browser.tabs.onTop;false
Open duckduckgo on new tab (defaults to about:newtab) browser.newtab.url;https://duckduckgo.com
Don’t warn if closing multiple tabs (defaults to true) browser.tabs.warnOnClose;false
Activate recent used tabs preview when <Ctrl><Tab> (defaults to false) browser.ctrlTab.previews;true
Activate all tabs preview when release ctrlTab on the "more" button browser.allTabs.previews;true
Do not display close button on tabs (defaults to 1) 0: Only on active tab 1: On all tabs 2: Not on any tab browser.tabs.closeButtons;2

Tab size of 3, expandtabs is enabled by default (defaults to 4) devtools.editor.tabsize;4
View source code in MacVim when <Cmd>U (defaults to '', false, '')

view_source.editor.args;-g
view_source.editor.external;true
view_source.editor.path;/Applications/MacVim.app/Contents/MacOS/Vim