How do I compress a PNG without losing transparency?
To compress a PNG, open FixDoks's Compress PNG tool and add your file. The tool reduces the image to an optimised palette of up to 256 colours, a technique called colour quantisation, which keeps transparency and can shrink screenshots and logos by half or more. Everything runs in your browser, and nothing is uploaded.
Compress PNG at a glance
| Input | PNG |
|---|---|
| Output | Compressed PNG, transparency kept |
| Processing | In your browser; your files are not uploaded |
| Price | Free, no watermark |
| Download | Free Google sign-in |
| Works on | Chrome, Edge, Safari and Firefox on Windows, Mac, Android and iPhone |
How to use Compress PNG
- Click Select images and choose your PNG files. Screenshots, logos and icons work best.
- Set the quality slider. Lower quality means fewer colours and a smaller file.
- Click Compress PNG. Transparent areas stay transparent. Download each file or a ZIP.
How does PNG compression work?
PNG is a lossless format, so saving it again at "lower quality" is not possible the way it is for JPG. A normal PNG stores every pixel with its full colour, which can mean millions of different shades. FixDoks uses colour quantisation: it studies the image, picks the best palette of up to 256 colours, and maps each pixel to its nearest palette colour. The result is saved as an indexed PNG, which needs far fewer bytes per pixel.
This is the same idea used by well known PNG optimisers. On screenshots, user interface images, charts, logos and illustrations the difference is very hard to see, while file size often drops by 50 to 80%.
Transparency is kept
The palette includes transparency levels, so logos on a transparent background, icons with soft shadows and stickers keep their see-through areas. There is no white box around them after compression.
Choosing the quality
- 90% and above: 256 colours, and the tool also tries a lossless re-encode and keeps whichever is smaller.
- 60 to 80%: a good balance for screenshots and graphics.
- Below 40%: very small files. Fine for simple icons and flat logos, but photos may show banding in gradients.
When PNG is the wrong format
If your PNG is actually a photo (a camera picture saved as PNG), it will stay fairly large even after quantisation, because photos have smooth gradients that need many colours. Converting it with PNG to JPG or PNG to WebP will usually make it much smaller. Keep PNG for images with text, sharp edges or transparency.
Target size mode
Switch to By target size to fit a limit in KB. The tool reduces colours first and then scales the image down if needed. If a PNG without transparency still cannot fit, it switches that file to JPG so you still get a file under the limit.
Screenshots are the best case
Phone and computer screenshots are usually saved as PNG, and they are often larger than they need to be, especially on high resolution screens where a single screenshot can be 1 to 3 MB. Because screenshots contain flat colours, text and interface elements, they quantise beautifully. At 70% quality most screenshots keep crisp text while shrinking dramatically, which makes them faster to share in chats, tickets and documentation.
Pixel size still matters
If a screenshot will be shown smaller than its real size, for example in a help article, resize it first with the image resizer. Halving the width and height quarters the number of pixels and typically halves the PNG size again after quantisation.