Compare two files without uploading either of them

Every other job in this cluster involves one file. A diff involves two, and they are the two most closely related versions of the same thing, which together say more than either does alone. The redline of an agreement shows exactly which clause was fought over and how far each side moved, which is often more sensitive than the final document either party would circulate.

Configuration diffs have the same shape and a sharper edge. Comparing a working environment against a broken one means handing over both, and the file that fixes the problem frequently contains the credential that was wrong in the other. You are not comparing two harmless documents; you are comparing the before and after of a live system.

Prepare both sides before you conclude anything. Normalise line endings, run both through the same formatter if one has been reformatted, and trim to the region you actually care about. A diff that reports every line as changed almost always means a formatting pass or a line ending difference rather than a real rewrite.

The offline test is particularly satisfying here because the operation feels like it should need a server and does not. Disconnect, paste both versions, and read the differences. Two confidential documents were compared and neither of them moved. If you would rather watch than disconnect, keep the network panel open while you paste: the second document produces no more traffic than the first, which is to say none at all.