KDiff3 vs Mergely

KDiff3 is a free, open-source desktop app for comparing and merging files and folders on Linux, macOS, and Windows. It can compare two or three text files or folders, showing differences line by line and character by character. For merge work, it can combine changes automatically and includes an editor for resolving conflicts, including three-way merges. Folder comparison and Git integration are supported. KDiff3 handles Unicode, UTF-8, and other file encodings; users can highlight or hide whitespace and comment changes, and print differences. It also supports version-control keyword and history merging, with network transparency through KIO. Its listed license is GPL-2.0-or-later. The Free plan costs nothing, and there is no free trial. Linux installation options include Discover or another AppStream store, a distribution package manager, or Flathub. The app page links to a handbook, forum, and bug-reporting page. KDE describes itself as an international community building and distributing free, open-source software since 1996.

Mergely is a browser-based diff and merge editor plus a JavaScript library for comparing two text documents. It places documents side by side and marks additions, deletions and changes. Differences are computed in the browser with JavaScript, without server calls for the comparison. The maker says imported documents stay in the browser unless saved or shared; saved diffs are public to anyone with the link and can be managed there. Developers can embed the library in web applications through its API. Documentation recommends the React component and describes CDN and webpack use, while the Angular component is out of date. Options include ignoring whitespace, case or accented characters, line numbers, wrapping and sidebars. The API can merge a whole document or a selected change across sides. Firefox, Chrome, Edge and Safari are supported. The open-source release is free under GPL, LGPL and MPL licenses; a Closed Distribution License is available by contacting the maker.