Make your JPEG photos smaller
JPEG is the format almost every camera and phone uses for photos, and it's a lossy format by design — it throws away some detail to keep file sizes manageable, and you can control exactly how much with a quality setting.
Lowering the quality setting compresses a JPEG further, trading a bit of fine detail (especially in busy areas like foliage or fabric texture) for a smaller file. Because JPEG compression is lossy, re-saving an already-compressed JPEG at a lower quality repeatedly can gradually introduce blocky artifacts — Downscale Image compresses from your original each time, so you get a clean result in one pass.
For photos you plan to print or archive, keep the original camera metadata — date, location, camera model — by turning on "Keep metadata" before downloading. For photos going on the web or into a form, leaving metadata off keeps things private and shaves off a little extra size.
Everything happens on your device. Your photos, including any personal or location data attached to them, are never sent to a server.