How to convert a PDF to PNG
- Drop a PDF into the box above. If it has a password, type it in; it stays on this page.
- Choose the background: White, like the page or Transparent.
- Pick a resolution (150 DPI for screens, 300 DPI for print) and, if you only need some pages, type them, such as
1-3, 5. - The pages are converted as soon as you change a setting. Download each PNG, or press Download all as ZIP.
A PNG with a transparent background
A PDF page is not a white sheet with ink on it: it is a list of drawing instructions (write this text here, fill this shape there), and the white is only what a viewer paints underneath. So the page can also be drawn onto nothing. With Transparent chosen, that is what happens: the text, lines, shapes and pictures are kept and everything between them is see-through. That is useful for a logo or a signature exported as PDF, a diagram you want to put on a coloured slide, or a stamp you want to lay over another document.
Our test logo, a blue circle, an orange square, a signature line and a line of text on a 300×150 pt page, came out at 300 DPI as a 1250×625 PNG that is 80% transparent, with the shapes fully opaque and their edges smoothly blended.
It cannot work on a scan. A scanned PDF is a photograph of the paper, and the white is part of the photograph. When we converted a page made from a scanned image with Transparent chosen, 0% of it became transparent, and the page says so instead of leaving you to wonder. For a scan, convert it on white and then use Make background transparent, which removes a background colour from a picture.
Why these PNG files are smaller
PNG is lossless, which is why it suits text and line drawings: no smudges around the letters as in a JPG. But a browser always writes a PNG the same way, with red, green, blue and transparency for every pixel, whatever the picture holds. A page of black text antialiased on white uses a couple of hundred shades of grey at most. This page checks what each page really contains and writes the smallest lossless form: grayscale, or an exact palette of only the colours used. It then opens the new file again and compares every pixel with the original before offering it.
| Setting | Plain browser PNG | This page | |
|---|---|---|---|
| 3 pages of text, A4 | 150 DPI, white | 1.44 MB | 509 KB (palettes of 244–247 colours), every pixel identical |
| 2 pages of coloured shapes and text | 150 DPI, white | 107.8 KB | 8.3 KB |
| Logo page, 300×150 pt | 300 DPI, transparent | 47.9 KB | 28.3 KB, 80% transparent |
| Scanned page (picture of text) | 150 DPI, transparent | 101.5 KB | 73.5 KB, 0% transparent (reported) |
| US Letter page of text | 600 DPI, white | 1.21 MB | 340 KB, made at 424 DPI (see below) |
“Plain browser PNG” is the same page drawn by the same engine and saved the usual way; we decoded both files and they hold exactly the same pixels. The difference is only in how they are packed. Photos inside a PDF have too many colours for a palette, so a page full of pictures shrinks less.
Resolution and printing
A PDF measures pages in points, 72 to the inch, so the pixel size is the page size times the DPI: an A4 page is 1241×1754 pixels at 150 DPI and 2481×3508 at 300 DPI. The line under the settings shows the size of page 1 before anything is made.
Each PNG also records its DPI (in the file’s pHYs field). Browser-made PNGs leave that out, and many programs then assume 72 or 96 DPI, so a 300 DPI page prints three or four times too large. With the DPI written in, an A4 page prints as A4.
There is one limit: browsers cannot draw a picture bigger than about 16.7 million pixels (the iPhone limit, which we use everywhere so a file made on a computer also opens on a phone). A US Letter page at 600 DPI would be 5100×6600, more than twice that, so it is made at about 424 DPI instead. The size line warns you before converting, the result is marked “reduced”, and the DPI written into the file is the real one, so it still prints at the right size. 600 DPI works in full for small pages such as logos, labels and cards.
Related tools
- PDF to JPG makes much smaller files for pages full of photos, or for forms that only accept JPG.
- Extract images from PDF pulls out the original pictures inside a PDF instead of drawing whole pages.
- Compress PNG shrinks a PNG further if you can accept fewer colours.
- JPG to PDF goes the other way, turning images into a PDF.