Big images, small effort
Modern cameras and phones produce large files: 12 MP photos are typically 2–5 MB as JPG, and 48 MP photos from recent flagship phones can exceed 10 MB. Screenshots on high-resolution displays saved as PNG are often 3–8 MB. A 1 MB target is a gentle compression for these files, enough to get past upload limits and keep email attachments manageable, without any visible change to the image.
Email attachments
Email providers limit the total size of attachments, commonly to 20–25 MB per message, and attachments are encoded in a way that makes them about a third larger in transit. Compressing each photo to under 1 MB means you can send a reasonable set in one email, and recipients on mobile data will thank you. Compressing also removes GPS location data, which you may not want to send to everyone on a mailing list.
How it works
Images are decoded in background Web Workers on your device: HEIC with libheif, JPG with MozJPEG, PNG and WebP with their own WebAssembly decoders. The tool searches for the highest JPG quality that fits under 1 MB using a quick binary search, which typically takes about seven encoding passes. If the image is already efficient and re-encoding would not help, the original image data is kept, with metadata stripped. If the image is so large that even a moderate quality does not fit, it is scaled down slightly.
48-megapixel photos
Recent phones can save 48 MP photos, which contain four times as many pixels as a standard 12 MP shot. These are the one case where a 1 MB target may require scaling down, usually to somewhere around 24–30 MP, which is still far more detail than any screen can show.
Choosing a smaller target
1 MB is a ceiling, not a goal. If you are preparing images for a website, a much smaller target such as 200 KB or 500 KB will make pages load faster. For full control over quality and format, use the main image compressor.