JPG, PNG or WebP?
There is no best format, only the right one for a given picture. Here is how to decide in ten seconds.
The choice follows the content, not a ranking
There is no best image format, only a best format for a given picture. Three cover nearly everything, and each is built around a different assumption about what the image contains.
JPEG assumes a photograph. Its compression discards the fine detail your eye is least likely to notice, which works beautifully on natural texture and gradual gradients and badly on sharp edges. It has no transparency. PNG assumes a graphic. It is lossless, keeps an alpha channel, and compresses large areas of identical colour extremely well — but on a photograph it produces a file several times the size of an equivalent JPEG. WebP covers both cases, with a lossy mode that beats JPEG by roughly 25-35% at matched quality and a lossless mode that beats PNG by 20-30%, keeping transparency in either.
A decision you can make in ten seconds
Does the image have large areas of flat colour, sharp edges, or text? Then it is a graphic: use PNG or lossless WebP. Compressing a screenshot as JPEG produces ringing around every letter, and no quality setting fixes it.
Is it a photograph? Then use JPEG or lossy WebP. Storing a photo as PNG typically triples or quadruples the file for a difference nobody can see. PNG to JPG is often the single largest page-weight saving available on an image-heavy site.
Does any part need to be transparent? Then JPEG is out, whatever else is true. Use PNG, or WebP if you want transparency at a fraction of PNG's size — that combination is exactly what neither older format offers.
The rule that matters more than the format
Lossy compression is not reversible, and this causes more avoidable damage than any wrong format choice. Every time a JPEG is opened and re-saved, the encoder compresses an already-compressed image and discards a little more. Do that repeatedly — a photo edited, saved, mailed, re-saved, re-sent — and the degradation compounds visibly.
Converting to a lossless format does not undo it. A JPEG with blocking artefacts converted to PNG is a faithful, lossless copy of a damaged image. What you gain is that no further damage occurs, which is exactly why PNG is the right working format while you are still editing.
The practical rule: keep the highest-quality original you have as your master, and treat every converted file as a disposable copy you can regenerate. If you find yourself converting the same image back and forth, stop and go back to the source.
Choosing a quality setting
When you do compress, the quality slider is not a percentage of fidelity — it sets how aggressively the encoder rounds off the frequency coefficients describing each block. The relationship to what you perceive is strongly non-linear, so the useful range is narrower than the slider suggests.
In practice, 90-100 is nearly indistinguishable from the original and rarely worth the size. 75-85 is where most web images belong: substantial savings, artefacts invisible at normal viewing distance. Between 60 and 75 degradation becomes visible on close inspection, acceptable for thumbnails. Below 60, reduce the image's dimensions instead of compressing harder — our resizer will do more for file size than the last few quality points, and without the artefacts. The image compressor shows a live preview so you can judge it yourself.