Diffchecker will compare text to find the difference between two text files. Just paste your files and click Find Difference!.

Folder Sync is described as 'An application to help you keep multiple pairs of folders in sync, quickly and easily. View differences between pairs of folders on screen using user defined coloured coding. Folder Sync allows you to utilise a fully automatic sync or manually manipulate the files yourself to' and is a Diff Tool in the backup & sync category. There are more than 50 alternatives to Folder Sync for a variety of platforms, including Windows, Mac, Linux, Web-based and Flathub apps. The best Folder Sync alternative is Beyond Compare. It's not free, so if you're looking for a free alternative, you could try SyncBack or KDiff3. Other great apps like Folder Sync are SyncToy, P4Merge, Diffchecker and Araxis Merge.
Diffchecker will compare text to find the difference between two text files. Just paste your files and click Find Difference!.

Pretty Diff is a language aware code comparison tool, beautifier, minifier, and parser for a variety of web oriented languages.

Pretty Diff is the most popular Self-Hosted alternative to Folder Sync.
Online Text compare is a browser based data compare tool that highlights the differences between two versions.
