What comes back?
Photos → WebP or a smaller image. Audio → MP3. Video → MP4. These conversions can reduce quality; your originals stay untouched.
Single HTML and Word (.docx) files → plain text, with formatting and images removed. Text and other files → gzip. Multiple files → one ZIP, keeping document formats and folder paths.
PDF and animated images aren't shrunk. HEIC and TIFF depend on your browser. Up to 5 files per drop, 25 MB each. Audio/video loads a 31 MB engine on first use.