Field guide
Resize by pixels, not kilobytes
Pixels describe the grid an image can display; kilobytes describe how efficiently that grid was encoded. They are related, but one cannot be substituted for the other.
01
Set width and height from the destination first. A 1200-pixel requirement is about dimensions even if two compliant photographs have very different byte sizes.
02
Choose format from content and transparency. JPEG usually stores photographs compactly, while PNG can be smaller for flat graphics and preserves hard edges exactly.
03
Use quality to meet a byte ceiling only after dimensions are correct. Lowering quality cannot make a 4000-pixel file satisfy a 1200-pixel specification.
04
Verify the saved file, not the settings panel. Read its actual dimensions, signature and byte count before uploading to a strict portal.