Convert PDF to WebP

There are three sensible ways to turn a PDF page into a picture and they are not interchangeable. JPG is small and smudges text. PNG is sharp and large. WebP is the one that does both jobs adequately, which makes it the right answer for the web and a slightly odd one anywhere else.

If you are showing a document preview on a site — a thumbnail of a report, the cover of something downloadable, a page embedded in an article — the image is competing with everything else on the page for load time.

A PNG of a text page is sharp and can easily be several hundred kilobytes. The same page as a WebP is typically a fraction of that, and the text still looks clean because WebP handles hard edges far better than JPG does. That combination is what nothing else offers.

This is the setting worth getting right, and it works differently here than for a photograph. A PDF stores instructions rather than pixels, so the page is drawn at whatever resolution you ask for, at full sharpness. The control is in dots per inch, from 36 to 600, and it starts at 150.

Convert the dpi into pixels before you pick one: an A4 page is 8.27 inches wide, so it comes out 595 pixels across at 72 dpi and 1240 at 150. The useful rule is to draw at roughly twice the size the image will occupy on screen, which for a thumbnail displayed 300 pixels wide means about 72 dpi — a long way below the default, and a much smaller file. Typing 600 in there gives you a 4960-pixel page nobody asked for.

WebP is forgiving of hard edges compared to JPG, but it is still lossy, and this path writes it at a fixed quality of 82 with no control on the page. There is nothing to push down and nothing to raise, which for a document page is the setting you would have chosen anyway — the file still comes out dramatically smaller than the PNG of the same page. If a page of eight-point footnotes looks soft, the answer is more dpi rather than more quality.

Anything leaving the browser. A page going into a printed report, a slide deck, an email attachment or somebody else's document should be a PNG, because some desktop software still does not read WebP and you will not be there to explain it. WebP is a format for the web, and this conversion is for pages that are staying there.

As with the other PDF conversions, one page is one image — the Pages box chooses how many — and the words become pixels, so the result cannot be searched or selected. If the text matters to a search engine, put the text on the page as text and use the image alongside it.

Thumbnailing one PDF is a moment; thumbnailing a library of them is the actual job. Dropping many files at once converts them one after another and returns them together, and because the work happens on your own machine there is no queue and no per-file cost to ration.

The free tier takes 100 files at a time and 100 MB per file, and below those the ceiling is your device’s memory — a desktop is far more generous than a phone. If a large batch stalls, splitting it in half is usually all that is needed.

Every current browser displays WebP, which covers the case this conversion is usually for — a thumbnail on a web page. Outside the browser the picture is patchier: some desktop image viewers, some older design software and a fair amount of corporate tooling still do not open it.

So WebP for a page you control, and PNG or JPG for a file you are handing to someone else. The conversion is the same work either way; the question is only where the image is going to be opened.