Side by Side Diff Checker
Two aligned panes, original on the left and changed on the right, with matching lines held level so your eye can track across. This is the view that reads best on a wide screen and when you are trying to understand a rewrite rather than just spot an edit.
This page opens in split view.
When side by side wins
Split view keeps both versions fully visible, so you can read the old wording and the new wording as complete thoughts. That matters for prose, for configuration where a value moved between keys, and for any change large enough that a unified view becomes a wall of plus and minus signs.
It costs horizontal space. On a narrow window the panes get cramped and unified becomes the more readable option.
Line diff and character diff
Line granularity suits source code, where a line is a meaningful unit. It reads badly on long single-line content such as minified JSON, where changing one character marks the entire line as replaced. Character granularity narrows it to the exact substring that changed, which is what you want for a typo hunt.
Nothing is uploaded
The comparison runs in your browser, which is the reason to use this rather than a hosted diff service when one side is a production config or a file from a private repository.
Diffing minified or generated files
Side by side loses its advantage on files with very long lines, because each pane wraps and the alignment that makes the view useful disappears.
Format or beautify both sides first. A diff of two formatted files is readable; a diff of two minified bundles is not, in any view.