The diff view

The diff view shows what Claude changed in one file: the file as it was before Claude’s first change in the session, against the file as it is now. It’s a window of its own, so it can stay open beside the conversation.

Opening it

Click a file in Changed files, or select it and press Enter. The line under the title says what the file is compared with: its contents before Claude’s first change in the session, or, with Working tree vs HEAD on, HEAD.

A file that changed since

When the file has changed since this session’s last change to it, by another tab, you or a command (Changed since), the view shows this session’s changes: from before Claude’s first change to how its last one left the file. There’s no Revert then, since that isn’t the file as it is.

With later changes shows the file as it is now instead, with what changed since, and Revert as usual. Click it again to go back.

Reading it

The view shows the changes with a few lines of context between them. Whole file shows every line.
Inline shows one column of lines with the old ones marked − and the new ones +. Side by side puts the old file on the left and the new one on the right.
Lines are colored by the file’s language, in the app’s light or dark theme. Files over 20,000 lines and binary files are shown without colors.
Long lines scroll sideways, with the scroll bar along the bottom, Shift and the mouse wheel, or a touchpad. Both sides scroll together, and the line numbers stay where they are.
Wrap lines wraps long lines at the width of the window instead, each side in its half when they’re side by side, so there’s nothing to scroll sideways. The next diff you open, in its window or a Files tab, starts the way you left it.
Line endings, a byte order mark at the start of a file and the newline at its end aren’t counted as changed lines (below).
A binary file says there’s nothing to show line by line, and a file that’s gone says it has been deleted.

What the lines don’t show

When no line changed, the view says what did in their place, as the file’s row in Changed files does (What the lines don’t show): “Only its line endings changed: CRLF to LF. The lines are the same on both sides.” The counts at the top say CRLF → LF. When lines changed too, a line under the file’s path says so: “Its line endings changed too: CRLF to LF”.

A line whose only change is its whitespace shows its spaces as · and its tabs as →, in a faint gray, on both sides, and the line under the path says so. A tab shown as → takes one character’s width.

When Claude changes the file while the window is open, choose Refresh in the … menu to read it again.

The file’s actions

The buttons along the top:

Side by side, Whole file and Wrap lines switch how the changes show.
With later changes, for a file that changed since this session’s last change to it (above).
Open in diff tool appears when you’ve set an external diff tool.
Open opens the file, as described below.
Revert file puts the whole file back (Reverting). Each change has a Revert of its own on its header.
Reviewed ticks the file and closes the window (Reviewed files).
… has Open in the OS’s app, Reveal in file manager, Copy path and Refresh.

The same actions are on the right-click menu of a row in Changed files.

Opening the file

Open opens the file in Claudette’s own editor (Project files), unless Settings → Files and diffs → Open files in is set to The app the OS uses for the file. When the file opens in Claudette’s editor, the diff window closes, so it doesn’t hide the editor behind it. Open in the OS’s app is always there when you want the app your system uses for that kind of file, such as an editor you can read with a screen reader.

Settings → Files and diffs → Open in the diff window can send Open elsewhere:

Opens the file, as Open files in says: the default, described above.
Opens the file in the app the OS uses for it, whatever Open files in says. The diff window stays open.
Opens the changes in the diff tool: the same as Open in diff tool, once you’ve set an external diff tool. A file whose earlier contents aren’t known opens as Open files in says, since the tool would have nothing to compare.

A file whose earlier contents aren’t known

The view shows the file as it is now, with nothing marked as changed, and says that what it held before isn’t known. It opens in the built-in view even when an external diff tool is set, since a tool would have nothing to compare it with.

Settings

Settings → Files and diffs → Open files in: where Open goes (Opening files from the conversation).
Settings → Files and diffs → Open in the diff window: whether the diff window’s Open goes there, to the OS’s app, or to your diff tool (Opening the file).
Settings → Files and diffs → Diff tool: which program opens a changed file’s diff (External diff tools).