For github web browsing, it is not shown as side by side as lots of diff tool does. Can I change the diff mode to side by side? I mean on the github web.
Github web does not have the feature yet.
You might be interested in term based diff tool cdiff, it has an option -s
to yield side-by-side diff.
To view changes not submitted yet, type
cdiff -s
To view change history in your workspace, type
cdiff -ls
To view changes from a pull request, pipe in the raw diff from the url, for example:
curl https://github.com/ymattw/cdiff/pull/11.diff | cdiff -s