Diffoniq shows the two sides next to each other, and one screen row always holds matching positions: the line on the left and the line on the right belong together. Where one side has something the other has not, its counterpart is left blank so the two sides stay aligned. That is why a single inserted line pushes nothing out of step.
Four colour pairs carry the meaning. All of them can be changed under Options › Colors; the descriptions below assume the standard scheme.
| Normal | Lines that are identical on both sides. |
| Difference | Lines belonging to a section that differs. The whole block is coloured, on both sides, so you can see at a glance how far a change reaches. |
| Inline difference | Within such a line, the characters that actually changed. This is the Show Inline Differences toggle — with it off, the line is simply marked as different as a whole. |
| Modified | Lines you changed in this session, by merging, pasting or clearing. They are not on disk yet. |
Difference sections are additionally set apart by horizontal separator lines, so the structure remains readable in a monochrome printout as well.
With Line Numbers switched on, each side carries its own numbering — the two sides drift apart by exactly the number of inserted or deleted lines, which is often the quickest way to see how much was added.
+ after the number marks a line you changed in
this session.+.An asterisk in front of the file name in the header marks a side with unsaved changes, and Save Modifications writes them out.
With Hide Matching Areas active (F7, on by default) long identical passages in the middle of the files are not shown at all. What remains is every difference plus a few identical margin lines above and below it for context. Nothing is lost — press F7 to see the files in full.
A directory or archive listing uses the same two panes, one row per file pair: