I setup Git to use Perforce’s P4Merge as the Git mergetool. P4Merge is cross-platform and free and quite good.

There are 2 things to consider when comparing them: 2 panel diffs and 3 panel merging.

P4Merge is very good at the second but not so much at the first.

Also, to this date it doesn't have an OS-X version for M1 CPUs.

I actually don't understand what people love about BC. The only thing I find it extremely useful for is the occasional files where inline diffs are practically mandatory, like CSVs. Other than that, I generally find it frustrating compared to TortoiseGitMerge, except perhaps for some very specific/unusual scenarios. In particular the line highlighting is annoying - instead of coloring the lines that were added vs. removed differently, it colors lines according to whether they're an "important difference" or "unimportant difference" (?!), which is borderline useless to me. What do people love about it so much?

I’ve been using BC since the early 2000’s, so probably more than 15 years. I know it backwards and forwards. If you set it up right, it is pretty powerful. It allows a lot of the stuff that other tools fail on to be overcome. Manual alignment is a dream. The rules based comparison is very nice. Ignoring unimportant differences removes pretty much all the white space differences. The ease of selecting arbitrary blocks and moving them left or right is powerful. I’ve tried both Windiff and kdiff3 and both have missing features.

Back before git, it was common to take a massive set of changes and merge them manually when merging branches, and BC was the only tool that made it painless for me.

I stumped up my own cash for a pro license and I use it almost daily even now.

I'll add the ability to specify and tag regexes ("comment", "timestamp", etc) on a file-type by file-type basis, and then specify various tags as "unimportant" for the current diff is super powerful.

It means you can do things like compare two system logs from different times and have it highlight you exactly the differences you care about.

Interesting. Have you tried TortoiseGitDiff? I'd be curious what you think of that in comparison if so.

Update: I just downloaded Meld. It literally takes ~half a second to change the cursor location when I click in a highlighted region, which is already making me dislike it. Is this normal?

The things that makes it borderline useless to you is actually one reason I like it so much. Makes it really easy to do code reviews and focus on what actually matters. Also, it was until somewhat recently the undisputed best 3-way merge tool. Meld gets close, but to me Meld's UI is sluggish and fuzzy (on Windows) while BC is snappy and sharp.

Maybe I need to try Meld at some point. Have you tried TortoiseGitDiff by any chance?

+1 for TortoiseGitMerge, which is my go-to tool these days. It's Windows only but not a problem for me since I mostly work in Windows.

My SO adores Meld, but she works with Linux. I tried using it but couldn't get used to it. She also makes fun of me (half in jest) because I use Tortoise Git instead of the command line...

I use TortoiseGit too, ever since I used TortoiseSVN back in the day. Highly underrated, and ridiculously powerful, I’ve practically never had to look up “how to do x” :)

And the theme is unusable on KDE dark theme to a red blue color blinded user.

winmerge is definitely the best windows-only open source app I've used. surprised it's never been ported to linux.

WinMerge for comparing two individual files. BeyondCompare for comparing deep nested directory structures.

Do you think the pro version of BeyondCompare is worth it compared to the standard one?

Yes. They often have sales, and I picked up Pro for about the price of Standard a few years back. If you see a sale, get Pro. If you are not worried about the pro feature set, get standard.

The other thing is that the trial used to be very fair. I don’t know if they changed it, but it used to give you “days of usage” not contiguous days. I once used it for about 5 months because the 30 day trial only counted the days I actually used it and I saved using it for when I really needed it, and used WinMerge when I could instead.

Beyond Compare is a gem.

Yes, I bought it years ago and it's been one of my goto tools. Worth every penny, plenty of features beyond just being a git mergetool.

Depends...

Pro version gives you 3 panel merging. If you use that a lot then it might be worth it. Or, instead, use P4Merge for it.

You need the Pro version to do a 3-way merge.