JPEG Quality Settings Explained: What 60% vs 90% Actually Looks Like
What that quality percentage slider actually controls, why the difference between 90% and 100% is invisible but the difference between 40% and 60% isn't, and how to pick a number instead of guessing.
A JPEG quality slider showing "75%" doesn't mean "75% as good as the original" — the relationship between that number and what you can actually see is not a straight line, and knowing roughly where the useful range is saves a lot of guessing.
What the percentage actually controls
JPEG compression works by discarding image detail the human eye is less likely to notice, more aggressively as the quality number drops. The percentage is a setting for that algorithm, not a direct measurement of visual quality — a 75 from one encoder and a 75 from another can look slightly different, since it's an instruction, not a universal scale.
The high end (85-100%): diminishing returns
Above roughly 85-90%, further increasing quality barely changes what's visible to the eye, but keeps meaningfully increasing file size — you're paying in bytes for a difference few people could spot in a side-by-side comparison. 100% (or 'no compression') is rarely worth its file size cost for anything that will be viewed on a screen.
The low end (below ~50%): where damage becomes visible
Below roughly 50%, compression artifacts — blocky patches, color banding, blurring around sharp edges — start becoming visible, especially in areas with fine detail or text. This range is usually only acceptable for thumbnails or previews where the image will be shown very small.
A practical range instead of a guess
For most web use — photos on a page, images in an article — quality in the 70-85% range is where file size drops substantially with a visible-quality cost that's hard to spot at normal viewing size. This is roughly the range most "smart" compressors default to, because it's genuinely close to the best tradeoff for typical photos.
The hidden second control: colour detail
The quality number is not the only thing happening inside a JPEG save. Most encoders also reduce colour resolution (called chroma subsampling) because eyes notice brightness detail far more than colour detail. Two tools at the same '80%' can make different subsampling choices and produce visibly different results around saturated edges — red text on a dark background is the classic casualty. It is another reason quality percentages are not portable between tools.
Quality for print is a different conversation
Screen guidance (70-85%) assumes normal viewing distance on a display. Print shows an image larger, closer and without a backlight, and smooth areas like skies can band visibly at settings that looked fine on screen. For photos headed to paper, stay at 90% or above, and remember the other half of the equation: enough pixels for the print size. A high quality setting cannot rescue an image that is simply too small for the paper.
The three-export test that settles it
Instead of memorising ranges, test your own image once: export it at 70, 80 and 90, then compare the most detailed area — hair, foliage, fabric, small text — at 100% zoom. Most people find the step where differences stop being visible, and that number becomes their personal default for similar photos. Two minutes of testing removes the guesswork permanently, for every photo that resembles the test one.
Quick tips
- Quality settings apply per-save — re-saving an already-compressed JPEG at a lower quality compounds the artifacts each time; keep an original if you'll need to re-export at a different quality later.
- The right quality also depends on the image itself: a busy, detailed photo hides compression artifacts better than a flat-color graphic or an image with fine text, which show them faster at the same percentage.
- If you're not sure what number to pick, File Doctor's automatic check judges this per-image instead of asking you to guess a percentage.
- Judge quality settings on your most detailed photo, not your smoothest — detail is where artefacts live.
- For text and line art, skip JPEG entirely: PNG removes the whole quality tradeoff.