Choose the destination before the number
A familiar size is useful only when it belongs to the place the image is going. Start with the card, thumbnail, post, video frame or form slot that must receive the file; then use its pixel box here. Resizing to a fashionable number and resizing again later spends detail twice.
Fit, cover and stretch answer different questions
Fit asks how large the whole picture can be inside the box. Cover asks how much of the picture must be cropped to fill every pixel. Stretch ignores the source proportions. For photographs, fit and cover are the defensible choices; stretch belongs to diagrams and textures where geometry is not identity.
Use the anchor as a composition control
When Cover removes a strip, the nine-point anchor decides which strip. Put a face near the top and choose a top anchor; put a product to the right and choose right. The preview shows the exact retained rectangle before any pixels are written.
Questions about the presets
Does a preset crop my picture automatically?
Only when Fill is selected and the source ratio differs from the target. A few destinations have a convention — a story fills the frame, a marketplace square is padded on white — and those presets choose that mode for you, visibly and undoably. Fit keeps the whole image and may produce a smaller second dimension; Pad keeps the whole image and adds a margin; Stretch forces both numbers and changes proportions.
Can I change the numbers after choosing a preset?
Yes. A preset writes width and height into the same fields you can edit yourself, and at most picks a fitting mode. Undo takes the whole step back, and the ratio chain can be switched on or off.
Why are there several square presets?
Because a 1080-pixel post, a 640-pixel profile image and a 256-pixel icon have different delivery costs even though their shape is identical. Choose the final display class rather than resizing the same square repeatedly.