Start with a sensible range, inspect the right details, and avoid treating one quality number as universal.

Quality is an encoder instruction

A quality slider tells an encoder how aggressively to trade detail for size. It is not a percentage of original quality, and the same number can produce different results in different encoders or browsers.

A starting value around the low eighties can be practical for photographic material, but it is only a starting point. The correct setting is the lowest value that remains visually acceptable for the actual destination.

Inspect the vulnerable parts

Do not judge only from a zoomed-out thumbnail. Look at edges, faces, hair, text, gradients, high-frequency texture, and areas near transparent boundaries. Those regions often reveal compression damage first.

  • Compare at the intended display size
  • Check 100% zoom for ringing and block artifacts
  • Inspect alpha edges against light and dark backgrounds
  • Confirm dimensions before blaming the encoder
  • Keep the source open for a true side-by-side comparison

Resize before chasing quality

An image that is much larger than its display slot wastes bytes regardless of quality. Reducing dimensions to an appropriate maximum can deliver a larger saving than lowering quality aggressively.

Resize from the best available source, then encode once. Repeatedly resizing and re-encoding an already compressed file compounds loss.

Smaller is not always better

A compressor can produce an output larger than the input when the source was already efficiently encoded or when the chosen setting is high. A trustworthy result view should show both sizes and let you decline the new file.

Metadata removal can also account for part of a size reduction. That may be desirable for privacy, but it is not the same as more efficient pixel compression.

A repeatable workflow

Choose the destination dimensions, encode at a moderate quality, compare the visual result, then step down gradually until artifacts become visible. Move back one step and keep that result. Record the setting only as a project-specific convention—not a universal rule.