WinMerge is an Open Source visual text file differencing and merging tool for Win32 platforms. It is highly useful for determing what has changed between project versions, and then merging changes between versions.

Features:

Visual differencing and merging of text files

Flexible editor with syntax highlighting

Handles DOS, UNIX and MAC text file formats

Unicode support

Difference pane shows current difference in two vertical panes

Location pane shows map of files compared

Highlights differences inside lines

File filters in directory diff

Moved lines detection in file compare

Shell Integration

Rudimentary Visual SourceSafe and Rational ClearCase integration

Archive file support using 7-zip

Plugins

Localizable interface via resource DLL

HTML-based Manual