KDiff3
File and folder comparison and merge tool
Araxis Merge
Two- and three-way file comparison, merging and folder synchronisation
Diffchecker
Online and desktop comparison of text, images, documents and spreadsheets
difftastic
Structural diff that understands syntax
diffoscope
In-depth comparison of files, archives and directories
Proxyman
HTTP(S) debugging proxy for macOS, Windows, Linux and mobile