Choose the right format first
JPEG works well for photos and complex scenes. PNG is useful for sharp graphics, transparency, and screenshots with text. WebP can be efficient for many web uses.
Changing format can matter more than changing quality settings. Test the format that matches the image type.
Inspect details after compression
Look at faces, product labels, small text, gradients, and shadows. These areas show compression problems first.
Do not judge only by file size. A tiny file that makes text unreadable is not a successful optimization.
Keep an original copy
Compression is usually lossy for photos. Save a separate optimized copy and keep the original in a safe folder.
If you need multiple sizes, create each size from the original rather than repeatedly compressing an already compressed file.
Practical example workflow
Start by deciding where the image will appear: a hero banner, product card, profile photo, form attachment, social preview, or email. Each location has a different useful size and crop. Preparing one giant file for every use case is slower for visitors and harder to review.
Make a working copy, resize it to the largest realistic display size, then export a compressed version. Open the exported file on desktop and mobile before publishing. Check small text, edges, faces, product labels, transparency, and color shifts. If those details are still clear, the smaller version is usually the better publishing file.
Quality checks before publishing
Use clear filenames, remove private metadata when the image is public, and keep the original file in a private folder. For client work, record the final width, height, format, and compression setting so the image can be recreated later without guessing.
For important uploads, test the image inside the actual platform instead of only viewing it locally. Some platforms crop thumbnails, recompress uploads, or reject transparent images. A quick final preview catches those problems before the file is shared publicly.