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The most often time I use diff (compare) is to compare a project file with the remote. Diff to requires you to select the 2nd file and thus doesn't work for remote files unless you fetch a copy outside the IDE first. Simpler if there was a "diff with remote" option that automatically compares the selected file with the same file on the currently selected remote config. Dreamweaver handles this by fetching a copy of the remote file to a temp file/folder and then comparing.