SaveImageAs: Save images as JPEG, PNG or WebP

Right-click an image, choose a format, and it saves. JPEG, PNG or WebP. The conversion runs on your computer. There is no account to create, nothing is uploaded, and no server is involved. Browsers saves whatever the site sent, in whatever format it happens to be in. If you need a PNG and the page serves WebP, you end up on a converter site or opening an image editor. This skips that step. IT CONVERTS FROM THE RIGHT SOURCE Pages usually display a shrunk, re-compressed copy of a much better original. Converting that to PNG only gets you a lossless copy of a thumbnail, which is not what anyone wants. So it looks for something better first. It reads the page's srcset and takes the largest version listed there. On Cloudinary-hosted images it strips the resize and quality parameters out of the URL, which makes Cloudinary hand back the original upload instead of the derivative. If neither of those works it falls back to the image you can see, so you are never worse off than before. A .WEBP FILE WILL ACTUALLY BE WEBP Browsers have an awkward quirk here. Ask it to encode a format it does not support and it hands back a PNG without raising an error. Extensions that do not check for this write PNG bytes into a file called something.avif, and you only find out weeks later when a program refuses to open it. SaveImageAs tests every encoder once when it installs, then checks each conversion against the real file type before anything gets written. Formats your browser cannot encode never appear in the menu. SOMETIMES THE RIGHT ANSWER IS NOT TO CONVERT Saving a PNG as a PNG copies the file as it is instead of putting it through another encode. The metadata survives and you avoid a second round of loss for no reason. There is also an "Original file" option in the menu, for when you want exactly what the server sent, animation included. THE FIDDLY PARTS Photos keep their orientation instead of arriving on their side. Transparent areas get filled with a colour you choose before any resizing happens, which avoids the dark fringe that otherwise shows up around edges. Large images are scaled down in stages so fine detail survives. SVG files are rasterised at a sensible size rather than a tiny one. SETTINGS Quality per format. An optional cap on the longest side. Filename templates using {name}, {ext}, {w}, {h}, {date}, {time} and {host}. Files can go straight to Downloads, prompt you each time, or land in a named subfolder of your choosing. PRIVACY Nothing is collected and nothing is sent anywhere. The only network request it makes is for the image you asked it to save, from the site already hosting it. Source code, MIT licensed: https://github.com/addyosmani/save-image-as