Illustrator is Saving files as a PDF by default.
Illustrator has been saving some of my large files as PDFs rather than Illustrator files (when I am just pressing Cmd+S) and the file is definitely not a PDF to begin with. This is frustrating because anything outside of the artboard is no longer in the file, the file must be opened as individual artworks, and all of the text is saved as individual letters in cases where text is typed along a path, or it's saved as individual words.
Alex
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Illustrator recently has changed the way the file type is chosen in the Save and Export dialogs — now it’s sticky. While it’s fine for Export, it’s not exactly OK for Save, and here’s a report about this.
However, tt doesn’t makes the bug reported fixed, but it can certainly lead to the same result. If this problem ever happens again and you are sure you picked the proper file type 0- drop a comment.