General

The procedure of setting Conkeror as your default browser varies by OS, and sometimes by program.

General information on the subject can be found here.

For more detail about launching conkeror including opening new tabs in existing instances see Invocation

Linux

Depending on your distribution these instructions may vary. In this example Debian was the target distribution but these instructions should work for Ubuntu too.

First off to allow selection of Conkeror as browser there needs to be a .desktop file. On debian this file contains insufficent mime types for the browser to be a possible target for urls. To fix this we need to create a new .desktop file. It could be placed in /usr/share/applications/ but if the file already exists then it will be overridden by OS upgrades so instead we are going to add it to your home directory.

first make sure the directory exists

mkdir -p ~/.local/share/applications/

then edit the file ~/.local/share/applications/conkeror.desktop and put the following contents in

[Desktop Entry]
Version=1.0
Type=Application
Terminal=false
Icon=conkeror.png
Name=Conkeror
Comment=Emacs like Web Browser
GenericName=Web Browser
Exec=conkeror %u
Categories=GNOME;GTK;Network;WebBrowser;
MimeType=text/html;text/xml;application/xhtml+xml;application/xml;application/vnd.mozilla.xul+xml;application/rss+xml;application/rdf+xml;image/gif;image/jpeg;image/png;x-scheme-handler/http;x-scheme-handler/https;x-scheme-handler/ftp;x-scheme-handler/chrome;video/webm;

Now that is done Conkeror can be selected as the default browser for desktop environments like GNOME and KDE.

Manual Configuration

If you are not using one of the major Desktop environments like Gnome or KDE and you still use xdg-open you can override the default xdg browser with xdg-mime.

xdg-mime default conkeror.desktop x-scheme-handler/http
xdg-mime default conkeror.desktop x-scheme-handler/https

To set it as the x-www-browser which may be used by some applications in Debian and Ubuntu to find the default browser.

sudo update-alternatives --config x-www-browser

For details about manual configuration of Emacs see the EmacsWiki