I too have wondered where to get a good free file comparison utility. Unfortunately I didn't find this information soon enough and ended up purchasing a commercial product called Araxis Merge. I say unfortunately only because it cost me some money. In all other respects it is a wonderful tool and I am very happy with it. I find it better than all the free choices mentioned below. The only free choice that comes close is the DiffMerge product from SourceGear.
Here's the short list of choices along with a brief comment. I haven't used any of these products extensively but used them just enough to get a quick impression:
- CSDIff - I found this product rather primitive. I did not like the single window difference format. I prefer the side-by-side dual window format much easier to use.
- DiffMerge - I found this tool pretty nice. This is the one I'd pick
- WinMerge - This produce landed somewhere in the middle. It seems to have most of the features and is graphical in nature but it didn't feel as nice as DiffMerge. My biggest complaint was the folder view. I seemed to have to manually dive down into each subfolder in order to see nested differences and this was very inconvenient.