Drop a photo, get a copy guaranteed under 1 MB at the best quality that fits. Nothing is uploaded — it all happens in your browser.
1 MB caps show up on email systems that reject heavy attachments, older ticketing tools, and upload fields that want "web-sized" images without being strict about it. Modern phone photos (2–8 MB, sometimes more at 48 MP) exceed it by default, which is the usual reason you're here.
Visually: nothing, in most cases. A megabyte holds a ~2800 px image at high JPEG quality, or your photo at nearly full resolution with quality in the high 80s. This is the "just make it fit" tier — the pixels you lose are ones JPEG was spending on noise. If the result reports no scaling and quality 85+, you can treat the compressed copy as equivalent to the original for anything except heavy editing or large prints.
Compress each to 1 MB and even a ten-photo email stays around 10 MB — under most attachment ceilings. Bonus: re-encoding strips each photo's GPS location and camera metadata, which you probably didn't intend to email a stranger anyway. Pixel-untouched metadata removal (no recompression) is the sibling tool PixWash.