The xdg-sanity script is built to replace your default web browser in your
desktop/XDG settings. It intercepts http/s URIs sent to the default browser by
xdg-open and sends it to the appropriate application. For example, it will
send image/jpeg MIME type files to your image viewer.
Installation
Arch Linux
I maintain a package on the AUR.
From Source
Dependencies:
- curl(1)
- handlr(1)
- tomcat(1)(optional; enables extensions)
Instructions:
Clone this repository and move the xdg-sanity binary wherever your operating
system stores locally-installed binaries. This is usually /usr/local/bin/ or
"$HOME/.local/bin/" for your user. Make sure the installation location is in
your $PATH.
Create an xdg-sanity.desktop file, placing it where your OS stores
locally-installed .desktop files, which is usually
/usr/local/share/applications or $XDG_DATA_HOME/applications for your user.
Set your default web browser to that .desktop file using handlr set.
Extensions
Extensions are written using TOML and are stored in either
/usr/share/xdg-sanity when installed from a package manager,
/usr/local/share/xdg-sanity when installed locally, or
$XDG_DATA_HOME/xdg-sanity for your user.
Extension support requires the installation of the tomcat(1) tool, which
parses TOML for the command line.
There are three kinds of extensions: MIME, replace, and scheme. MIME extensions are parsed first and replace the MIME type of the content being fetched. Replace extensions change the URI passed to the command to another. Scheme extensions replace the protocol by which the URI hostname is being accessed.
The type of the extension depends on the file name. MIME extensions should have
a name ending in .mime.toml, replace extensions should have
.replace.toml, and scheme extensions should end with .scheme.toml.
Here's what a MIME extension looks like:
$ cat $XDG_DATA_HOME/xdg-sanity/youtube.mime.toml
[replace]
urls = [ "youtube.com", "youtu.be" ]
[with]
mime = "video/vnd.youtube.yt"
what a replace extension looks like:
$ cat $XDG_DATA_HOME/xdg-sanity/youtube.replace.toml
[replace]
urls = [ "youtube.com", "youtu.be" ]
[with] 
url = "https://piped.mint.lgbt/"
and what a scheme extension looks like:
$ cat $XDG_DATA_HOME/xdg-sanity/spotify.scheme.toml
[replace]
urls = [ "spotify.com" ]
[with]
scheme = "spotify://"