Which format should this image be?
It encodes your file three ways and shows you the real numbers, rather than a rule of thumb.
JPG, PNG, WebP, HEIC, AVIF and BMP. Your file is processed on your device.
Which image format should I use?
The advice everyone gives, and why it is not enough
JPEG for photographs. PNG for logos, screenshots and anything with sharp edges or transparency. WebP for the web because it is smaller. All of that is true, and all of it is a statement about categories of image rather than about the file in front of you.
Real files do not sort themselves into those categories cleanly. A screenshot of a video is a photograph wearing a screenshot’s name. A product photo on a plain white background has large flat regions that PNG handles well and photographic detail that it does not. An illustration with soft gradients can go either way depending on how soft.
Rather than guess which category yours falls into, this page encodes it three ways and reads the file sizes off. The recommendation that follows is derived from those numbers plus two facts — whether the image has transparency, and where it is going — and it shows its reasoning, so you can disagree with it.
What the file sizes tell you about your image
The comparison is diagnostic as well as practical. If PNG comes out smaller than JPEG, your image is not photographic: it has large areas of identical colour and hard edges, which is the signature of a screenshot, a diagram or a logo. Those are exactly the images JPEG damages most visibly, with faint halos along every edge.
If PNG comes out several times larger, it is photographic — continuous tone, noise, no two adjacent pixels quite the same — and lossless compression has nothing to work with. Then the only question is JPEG or WebP, and that is a compatibility decision rather than a quality one.
Compatibility is the part the numbers cannot show
JPEG and PNG are accepted by essentially everything ever written. WebP is accepted by every current browser and refused by a long tail of other software: older versions of design tools, some print workflows, a fair number of upload forms whose validators were written before 2020, and the occasional email client.
So the rule is about control. On a website you own, use WebP and take the saving. On a form someone else built, use JPEG or PNG, because a rejected upload costs more than a few hundred kilobytes ever will.
Transparency settles it on its own
If your image has transparent areas, JPEG is not a candidate at any file size. It has no channel to store them in, so the transparent regions become solid colour — white if you are lucky, black if you are not. That is why the tool checks for alpha first and takes JPEG off the table when it finds any, rather than recommending it on size and letting you discover the problem later.
Size is not the only axis
PNG is lossless: every pixel comes back exactly. JPEG and WebP are not, and each save discards a little more, which is why editing a JPEG repeatedly degrades it in a way that editing a PNG does not. If a file is a working copy you will open and re-save several times, that matters more than the megabytes — keep the master lossless and export a lossy copy at the end.
Once you have decided, the converter will do the conversion with a file size limit at the same time, and the longer comparison covers how the three formats work.
Common questions
- Why measure instead of following the usual advice?
- Because "PNG for graphics, JPEG for photos" is a statement about averages and you have a specific file. A screenshot of a photograph behaves like a photograph. A poster with a photographic background behaves like a photograph. A chart with an anti-aliased gradient sits somewhere in between and no rule of thumb will tell you where. Three encodes take a couple of seconds and produce an actual answer.
- Is WebP always smaller than JPEG?
- Usually, and not always. At the same quality setting WebP is typically 20–35% smaller on photographs, less on images that are already small, and occasionally slightly larger on files where JPEG’s particular tricks happen to fit the content. That is exactly why this page encodes your file rather than repeating the average.
- Should I use WebP everywhere then?
- On your own website, yes — every browser in current use displays it. Anywhere you do not control, be careful: a minority of upload forms, older desktop software, some printers and a number of internal business systems still reject WebP outright, and a file that will not open is worse than one that is 30% larger.
- Why is AVIF not included?
- Because browsers can display AVIF but cannot reliably create it. FileBelow does all of its work on your device, so it can only offer formats your browser can actually encode, and a converter that produces AVIF on some machines and fails silently on others would be worse than one that does not offer it. Reading AVIF works — you can convert one to JPEG here.
- What quality setting is used for the comparison?
- Eighty-five per cent, for both lossy formats. Comparing formats at different quality settings measures the settings rather than the formats. PNG has no quality setting at all — it is always lossless — which is why it is usually the largest of the three and why that is not a fault.