Choose the right format
JPG is often the best choice for photographs, while PNG is useful when transparency matters. WebP can also be a strong option where browser support is acceptable.
Resize to fit the real use case
Large dimensions create large files. If an image only needs to display at a smaller width, resizing it before upload can dramatically reduce its file size.
Balance quality and size
Reducing quality slightly often leads to a much smaller file with minimal visible change. The best result depends on how the image will be used.