Every platform has its own dimensions, ratios and file-size limits, and getting them wrong means your image is cropped badly, rejected outright, or displayed blurry. Worse, the numbers change as platforms redesign.

These articles collect the current specifications for the places images actually go — social feeds, e-commerce listings, app stores, business profiles, meeting backgrounds, email signatures — along with the rules that outlast the numbers: keep the subject in the central 80% because every platform crops differently, check the file-size cap separately from the pixel dimensions, and never upscale to reach a required size. Several also cover form uploads, where a photo, a signature and an ID scan each carry different constraints.