Most reviewers click through GitHub's diff UI. Senior reviewers use git diff locally for speed and precision.
Useful flavors:
git diff main...feature — three-dot: only what feature added since the merge base. The "what's this PR doing" view.
git diff main..feature — two-dot is the same as git diff main feature: the net difference between the two tip snapshots. If main moved on after you branched, its changes show up here as inverted diffs, which muddies a review. Rarely what you want.
git log -p main..feature — commit-by-commit patches. Best for multi-commit PRs.
git diff --stat main...feature — file change summary. Read this first to know what's touched.
git diff --word-diff=color — word-level diff. Brilliant for prose, config files, JSON.
Search within a diff:
git diff main...feature -- src/auth/ — limit to a path.
Reviewers who do this locally finish PRs in 30% the time of GitHub-UI-only reviewers.