I've found reviewing code on GitHub alone isn't sufficient.

I also:

1. Run the code. I check the visual design, user experience, perf, accessibility, security.

2. I read and navigate the code in the editor to assure the files feel organized logically.

It's remarkable how different my mindset is when I review code in my editor and actually run it instead of merely reading a diff.

I catch more mistakes and consider many more types of concerns that are hard to notice in a simple diff.

It's surprising how many replies below are basically "sure, that would be nice, but who has the time to review code properly?"

Code review is like testing. It's an investment in quality.

To me, if the team doesn't have time to do thorough code reviews, it's out of control.

Some seem to think their boss would get mad if they took the time to do thorough code reviews.

My take: I don’t ask permission to do my job well.

So, if my boss thinks code reviews aren’t important, I need to sell him on why they’re critical.

Some people have suggested doing pair programming instead of code reviews.

My take? Pair programming is useful for challenging tasks, but overkill for most.

And even if I pair program, code reviews by the rest of the team remain valuable.