PNG or JPG: Which Belongs in Your PDF?

First, you probably shouldn't convert anything

The best format for a PDF is usually the one the file already is. Converting a camera JPEG to PNG cannot bring back detail that JPEG already discarded — you just get a much bigger file containing the same pixels. Converting a screenshot's PNG to JPEG does permanent damage to the letterforms, and nothing later in the chain undoes it.

So the real choice happens earlier than most people think: when you export a chart, save a screenshot, or pick a camera setting. If the files already exist on your disk, the right move is to feed them into the PDF exactly as they are and let the converter leave them alone. The converter on this page does that: a baseline JPEG is copied into the PDF byte for byte, and a PNG is rebuilt with lossless compression, so no pixel changes value.

What each format actually does to your pixels

PNG is lossless. It records every pixel exactly and squeezes the file by finding repetition. That works brilliantly on flat colour, straight lines and identical rows of pixels, and hardly at all on the fine random noise that fills every photograph.

JPEG works the other way round. It throws away detail people are bad at seeing, and it does this in small square blocks. Smooth gradients and gentle texture survive that treatment almost perfectly. Hard, high-contrast edges do not — which is why black text on white, compressed as JPEG, ends up with a faint grey speckle around each letter.

A photograph is almost entirely soft edges, so JPEG's damage is invisible. A screenshot is almost entirely hard edges, so it is the worst possible input for JPEG and the best possible input for PNG.

Choosing PNG or JPG for a PDF: the decision table

One useful exception: a screenshot that is mostly a photograph — a picture opened full-screen, say — behaves like a photograph. JPEG is fine there.

Why your PDF is so large: usually a photo saved as PNG

This is one of the most common causes of a PDF that will not go through email. A photograph stored as PNG can easily be around ten times the size of the same photograph as a JPEG, and there is nothing visible to show for it. Forty holiday photos exported as PNG become a PDF of hundreds of megabytes; the same forty as JPEG land somewhere sensible.

It usually happens by accident. A screenshot tool, a design app or a "save image as" default hands you PNG, you never look at the extension, and the size only becomes obvious at the end. If your PDF is already too big, converting the source photos to JPEG first is the fix that costs you the least visible quality — more ways to shrink an oversized PDF if that is where you are.

The reverse mistake is quieter but worse. A PNG screenshot re-saved as JPEG looks fine at 100%, then falls apart the moment anyone zooms in or prints it, and by then the original is often gone.

What a PDF does with each format on the way in

PDF has native room for JPEG data, so a baseline JPEG can be written into the page exactly as it is, byte for byte. Nothing is decoded, nothing is re-compressed, and there is no second round of loss. Your PDF page literally contains your original JPEG. Three kinds cannot take that route and are decoded and re-encoded once instead: CMYK JPEGs, progressive JPEGs, and photos whose EXIF says they are mirrored. The tool tells you when that happens.

PNG has no such slot, but it is still handled without loss: no pixel changes value, the data is simply re-compressed with the PDF's own lossless compression. That is why a PNG page can come out a little smaller or a little larger than the file you started with, while looking identical.

Every other format — HEIC, TIFF, WebP, AVIF, GIF, BMP, SVG — has no place in PDF at all, so it must be decoded and re-encoded once, as JPEG for photographs or PNG for graphics and transparency. That is one re-encode, and it is worth protecting. If you convert your iPhone HEIC photos to JPEG yourself first, that is still only one re-encode — the converter embeds the JPEG you hand it without touching it. What you lose is control: whatever quality setting the other tool used is baked in before we ever see the file. Hand over the originals and the single re-encode happens here, at high quality.

Transparency, and why your logo still sits on white

JPEG cannot store transparency in any form. Save a logo with a transparent background as JPEG and the transparent area gets filled in, usually white, occasionally black. There is no setting that changes this — the format has no channel for it.

PDF can carry transparency, using soft masks, and a PNG's transparent areas survive into the page. The catch is that PDF viewers paint the page white behind everything, so a transparent logo on an otherwise blank PDF page looks exactly like one flattened onto white. The difference only shows up when the page has a coloured background, when the PDF is placed inside another document, or in some print workflows.

If you need the logo to sit on a specific colour, put it on that colour in an image editor before converting. Deciding it yourself is more predictable than hoping every viewer paints the same background.

The 30-second check when you're not sure

1. Ask where the file came from. Out of a camera means photograph, means JPG. Out of a screen capture, a spreadsheet, a design tool or a PDF export means PNG.
2. Zoom to 300% or 400% on the sharpest edge in the picture. Grey speckle around black text means the file has already been through JPEG, and converting it to PNG now will preserve the speckle rather than remove it.
3. Still unsure? Make the PDF both ways and compare. In a browser converter that takes a minute, costs nothing and settles the argument with your own eyes rather than a rule of thumb.

The converter on this page copies a baseline JPEG in byte for byte and rebuilds a PNG losslessly, tells you afterwards which route each file took, and never uploads anything — the whole thing runs in the tab. If your screen captures are tall enough to run off the page, splitting a long image across pages is the guide for that shape of image.