Gemini's upload rules are the loosest of the big three and that is exactly why people trip on them. Gemini Apps accept up to 10 files in a single prompt (subject to availability), and non-video files can be up to 100MB each, so almost nothing fails on size — which means the failure mode is different. If you upload ten 40MB photos you are dragging a 400MB prompt through a browser upload and a model pipeline that tiles every image into 768x768 chunks at 258 tokens per tile. The token math is the real constraint: images with both dimensions at or under 384px cost a flat 258 tokens, and anything larger gets tiled, so a 3000x2000 photo becomes six tiles and 1,548 tokens while a 1200x800 image becomes one tile for the same information. Gemini also warns that very large uploads can produce answers that miss details scattered through the content, which is the opposite of what people expect from sending more pixels. The fix is to resize each image to roughly the size Gemini actually processes, then compress so the batch uploads quickly. Skwish compresses and resizes images locally in your browser with a live before/after readout per file. Batch the set, export a ZIP. Nothing is uploaded to a server.