Open a screenshot, save it as PNG, and you might get a 3 MB file for an image that is mostly grey. Save the same screenshot as JPG and it drops to 200 KB. PNG has a reputation for being bloated, and the reputation is mostly accurate — but the reasons are worth understanding before you switch formats blindly.
The cost of being lossless
PNG never throws away pixel data. That is its main feature and the source of its biggest weakness. JPG and WEBP can be much smaller because they decide what parts of an image you will not notice losing. PNG cannot make that decision, so it has to encode every pixel exactly as it is.
What actually makes PNGs large
- Photographs. Lots of unique colours and gradients give PNG nothing to compress.
- High resolution. PNG cost scales linearly with pixel count.
- Noise and grain. Even imperceptible noise prevents PNG from finding repeating patterns.
- 32-bit colour depth. RGBA at full bit depth is roughly 4 bytes per pixel before compression.
- Lack of optimisation tools. Many image editors save PNG at a low compression level by default.
How to make PNGs smaller
- Run the file through a PNG optimiser. Tools like oxipng or pngquant can shrink a PNG by 30–70% without changing how it looks.
- Reduce the colour palette. If your image only uses 50 colours, save as 8-bit palette PNG instead of 32-bit RGBA.
- Strip metadata. EXIF and colour profile chunks add weight you usually do not need.
- Resize. Halving the dimensions cuts pixel count by 4×.
- If transparency is not required, switch to JPG or WEBP. The savings are enormous.
When to switch formats
- Photographs: switch to JPG, WEBP, or AVIF.
- Hero images on websites: switch to WEBP or AVIF.
- Screenshots: keep PNG if you need crisp text, switch to lossless WEBP for similar quality at smaller size.
- Tiny icons: keep PNG, savings are negligible.
Frequently asked questions
Is PNG always bigger than JPG?+
For photographs, almost always. For simple graphics with few colours, PNG can be smaller than JPG.
Does compressing a PNG lose quality?+
No. PNG compression is lossless. Optimised PNGs are pixel-identical to the original.
Why does my PNG screenshot have so many colours?+
Modern OSes use subpixel rendering and anti-aliasing for text, which produces thousands of subtle colour variations. That is what defeats PNG's palette compression.