Image compression is a balance between transfer size and visual quality. The best workflow does not simply push a quality slider to the lowest possible value. Dimensions, format, image content and the actual display size all matter.
Resize first
If a website displays an image at 900 pixels wide, sending a 4000-pixel original wastes bandwidth. Choose a sensible output dimension first, then compare compression settings.
Choose the format
Photographs often compress well as JPEG or WebP. Transparency may make PNG or WebP more appropriate. Screenshots and small graphics should be checked visually because sharp edges and text reveal artifacts quickly.
Compare at the real display size
Inspect the compressed result at approximately the size visitors will see. Look for halos, blurred text, blocky areas and damaged fine details. A large percentage reduction is useful information, but it is not a quality score.
Use the Image Compressor & WebP Converter to compare original and output sizes while processing images locally in the browser.
Keep originals
Keep a high-quality source file separate from the web copy. If the design changes later, you can regenerate the optimized version instead of compressing an already compressed image again.
Measure the result
For important images, record dimensions, format and output size. Over time this creates a repeatable workflow rather than a series of guesses.
Conclusion
Good compression is controlled reduction. Resize first, choose a suitable format, inspect the visual result and keep the original source.