Match the destination
Use 1:1 for avatars, product tiles and compact grids. A 4:3 crop works well for general editorial images because it leaves room around the subject without becoming too tall. Use 16:9 for video covers and wide banners, and 3:4 for portrait-oriented listings or profile imagery.
Confirm the exact component ratio in the final layout. Platforms may display one ratio in a feed and crop it again in a preview, so keep critical content away from the outer edge.
Protect faces, text and product details
Place the main subject with enough breathing room for responsive cropping. Avoid cutting through joints, the top of a product or the baseline of visible text. When the image includes embedded words, preview it at mobile size to confirm they remain readable.
A centered crop is not always the strongest crop. Move the selection to preserve the direction a person is looking or to leave space where the page will place a title.
Crop first, compress second
Cropping removes pixels permanently from the exported copy. Keep the source file, produce the correct composition, and then decide whether the delivery file needs lossy compression. This avoids compressing pixels that will later be discarded.
When maximum fidelity matters, leave compression off in the crop tool. The browser still has to encode a new file, but the tool will not intentionally lower the JPG or WebP quality setting.