FileMerge Overview
FileMerge is Apple's graphical file comparison and merge tool for macOS, included with Apple's developer tools. It lets you compare two files side by side, with differences highlighted and connected across the two panes so you can see exactly what changed, and it provides a merge view for combining changes and resolving conflicts into a single output file. Developers commonly use it to review code changes and to settle merge conflicts from version-control systems, since it can be configured as the external diff and merge tool that opens when needed. FileMerge presents a clear, uncluttered interface and supports choosing, per difference, which side's change to keep. Because it is part of Apple's developer tooling, it is installed alongside the Xcode developer tools rather than as a separate product. This page links to the official Apple developer tools download.
