PNG vs JPG vs PDF: what each one is for

The short answer: two picture formats and one page format

Think of it like this. A JPG and a PNG are both a picture made of tiny coloured dots. A PDF is a document: it can hold one page or hundreds, and each page can have typed text, pictures, or both. Here is the whole comparison in one table.

The rest of this post explains each row, with the real file sizes we measured in our tests, and a short guide to choosing. To change from one to another, use PNG to PDF, JPG to PDF, PDF to PNG or PDF to JPG. They all run in your browser.

A PDF is a box, not a better picture

People often ask which is "higher quality": PNG, JPG or PDF. The question mixes two kinds of thing. PNG and JPG are ways to write down a picture. A PDF is a container, and it can hold either of them.

That is why turning a picture into a PDF doesn't change how it looks. A JPG goes into the PDF with its picture data copied as it is, and a plain PNG does too. Our JPG to PDF tests show it: 20 photos of 12 megapixels each, 62.4 MB together, made a PDF of 62.4 MB. Nothing was packed again, so nothing was lost, and the PDF was about as big as the photos.

It works the other way too. A PDF page can hold a JPG, a PNG, typed text with fonts, or a mix. The PDF doesn't decide how good the page looks. What is inside it does:

• A typed PDF (a bank statement, a form filled on a computer) holds real text. It stays sharp at any zoom, and you can search and copy it.
• A scanned PDF holds pictures of paper. It is as sharp as the scan was, and you can read the words but not search or copy them. Our tools don't recognise text in pictures.
• A PDF made from photos or screenshots is the same as a scanned one: the pages are pictures.

So a "PNG page" and a "PDF page" can hold exactly the same dots. The PDF adds the things a picture file can't: page order, one file for many pages, and the same look everywhere.

Lossless PNG and lossy JPG, in plain words

Both formats make a picture file smaller, but they do it in opposite ways.

• PNG is "lossless". It stores the picture in a shorter way, but unpacking it gives back every dot exactly. Open it, save it again as a PNG, and it is still perfect.
• JPG is "lossy". To keep files small, it leaves out fine detail the eye hardly notices. The first time, the loss is small. But each time a JPG is opened and saved again as a new JPG, a little more detail goes. Text turns soft, edges smudge, and faint blocks appear.

This matters for what you do with a file. Edit a JPG ten times and save it each time, and it gets worse each time. Copy it ten times, and it stays exactly the same, because a copy doesn't change a single dot. It is also why a photo that has passed through several chat apps often looks softer: an app that makes a photo smaller saves it again, and every save takes a little more detail.

Another thing JPG can't do is hold see-through parts. A PNG can: the checkered background an editor shows behind a logo or a signature. A PDF page is paper, so when a see-through PNG goes into a PDF, the see-through parts become white. Read Transparent PNG to PDF: what happens to the background if you have a logo or a signature.

What the sizes look like in real files

The two formats are good at different things, so the size of a file depends on what the picture is. These are measured numbers from our tests, each from the tool page named in the last column. They are samples: your files will differ.

Two things stand out. First, the PDF is almost the same size as the pictures inside it, within about 1 KB in the first rows, because nothing was compressed again. Second, the same format can be big or small: a photo page is huge as a PNG and tiny as a JPG, while a chart is tiny as a PNG.

Pixel size alone doesn't decide it either. In our tests, one computer screenshot of 1920 × 1080 was 214 KB as a PNG, and a busier screenshot of the same 1920 × 1080 was 882 KB. A calm screen with plain colours packs small, and a screen full of detail doesn't. These were two different screenshots, so don't compare them as the same picture.

Which one to use for what

Start from what you are doing, and the choice is nearly always clear.

For a photo of a document, the shortest path is photo, then PDF. Our photo to PDF on your phone post walks through it. If a form then says "under 100 KB", the Compress PDF to 100 KB page makes the sharpest version that fits.

The simple rule from our PNG page works for most things: photos as JPG, everything with text, lines or flat colours as PNG. If you have both kinds, mix them in one PDF. Each picture goes in its own best way.

Changing from one to another, and what you can't undo

Moving between these formats is easy, but some moves can't be reversed. Here is each one.

• Picture to PDF. Safe. PNG to PDF and JPG to PDF copy plain pictures in as they are. The PDF is as good as the picture, and as big.
• PDF to picture. PDF to PNG and PDF to JPG draw each page as a picture. A typed page is best as a PNG, a scanned page as a JPG. The post PDF page to image: PNG or JPG? has the details. The text in the picture can no longer be searched or copied.
• JPG to PNG. The file gets bigger, but the lost detail doesn't come back. A PNG made from a JPG holds the JPG's soft dots, perfectly. That helps only if you plan to edit it many times.
• PNG to JPG. Smaller, but some detail goes, and see-through parts must become a solid colour. Fine for a photo, not great for a sharp screenshot of text.

One more thing to avoid: renaming a file doesn't convert it. If you change photo.png to photo.jpg, the file still holds a PNG's data. Some apps open it anyway, some complain, and it won't be any smaller. Use a converter instead.

Common mix-ups, cleared up

"PNG is always better quality than JPG."

PNG never loses detail, but that doesn't make it look better. For a photo, a good JPG looks the same to the eye and is far smaller. That is the 889 KB against 74 KB above.

"A PDF is a higher quality picture."

A PDF only keeps what you give it. A blurry photo in a PDF is a blurry page. The tool does not sharpen it.

"My scanned PDF has text I can copy."

Only if the PDF holds real text. A scan of paper is a picture, so the words can be read but not searched or copied.

"A smaller file is lower quality."

Not always. A chart saved as a PNG is only 12 KB and is perfect. A photo page as a PNG is 889 KB and no sharper than the 74 KB JPG. Size depends on the kind of picture.

"I need a PDF for everything."

No. For one photo that goes into a chat, a JPG is the lightest and simplest. A PDF is the right choice when pages must stay together, or a form asks for it.

Changing formats without sending your pictures anywhere

The pictures people convert are often private: screenshots of chats and bank apps, photos of ID cards and certificates. Many online converters upload them to a server first. Our tools have no upload step and never send your pictures anywhere: your own browser does the work. The page contacts only this site and Google's ad service, which shows the ads that keep the tools free, and our code never gives your files to the ad code. The privacy policy has the details.