ChatGPT's image limit is 20MB per image, which sounds generous until you check the rest of the rules. Uploads run at 80 files every three hours on paid plans, and free accounts get 3 file uploads per day — a failed attempt can count against that. And the number of images you can add to one conversation depends on how large they are and how much text you attach alongside them, so a set of uncompressed photos hits a wall long before the byte cap does. The practical result: a 12MB camera JPEG goes through fine and still makes the conversation slow and clumsy to work with, while a downscaled version of the same photo answers the question just as well. Most ChatGPT image tasks — reading a receipt, checking a layout, comparing two screenshots, describing a diagram — need roughly 1000 to 2000 pixels on the long edge, not a 12-megapixel file. Skwish compresses and resizes images locally in your browser with a live before/after readout per file, so you resize to the size the model reads and keep the bytes low in one pass. Batch a folder of screenshots, export a ZIP. Nothing is uploaded to a server.