Example: a 2880 × 1800 Retina screenshot of this page
Measured with PicoDiet's default settings. At the same quality target, a JPEG of this screenshot needed 359 KB, against 58.8 KB as PNG, so PNG was the better choice here.
Why PNG files get so big
PNG is lossless: it stores every pixel exactly. That is right for screenshots, logos, icons and images with transparency, where JPEG would blur sharp edges and text. But most PNGs store far more colour information than the eye can use. A screenshot with a few gradients can carry tens of thousands of distinct colours, and a tool export may be saved at full 32-bit depth even when it holds only a few hundred.
The usual fix is to reduce the image to a palette of up to 256 colours, which is what TinyPNG and pngquant do. The question is how many colours each image needs. Too few and gradients band and anti-aliased text gets jagged; too many and the file stays big.
How PicoDiet compresses PNG
PicoDiet tries palettes of different sizes and keeps the smallest one that still looks the same as your original (quality score 80 by default), with a check that no small area, such as a line of text, gets visibly worse. When no palette is good enough, as with a photo saved as PNG, the image stays full colour. How the score works
Transparency is kept, including soft edges and shadows. The result is a normal PNG that every browser, editor and app opens.
How to compress a PNG
- Drop your PNG files above, choose them, or paste a screenshot straight from the clipboard with Ctrl+V or ⌘V.
- Each file is compressed right away at quality 80. Raise the quality score to keep more detail in graphics, or lower it for smaller files.
- Open an image to compare it with the original, zoomed in, then download it or all of them as a ZIP.
What the quality slider means for PNG
| Score | What you see | Good for |
|---|---|---|
| 90–95 | No visible difference at normal size | UI assets, logos, images you will edit again |
| 80 | The same at normal viewing size | Screenshots in docs, websites, chats |
| 70 | Slight banding in smooth gradients up close | Previews and thumbnails |
When to convert a PNG photo to JPEG
For photos you plan to share or put on a website, JPEG is usually much smaller than PNG. In our test, a 2048 × 1683 photo was 3.79 MB as PNG and 160 KB as a JPEG that scored 80: 24 times smaller, and you can't tell them apart. Choose Auto above the results and PicoDiet will switch photos to JPEG (or keep PNG or WebP when there is transparency). For the web, WebP and AVIF are other options in Options.
What happens to your images
Uploaded over HTTPS to the nearest of our servers, processed automatically, and deleted within 3 minutes after you finish. Never shared, sold or used for training. No account needed. Privacy policy
PNG questions
Is PNG compression lossless?
The PNG format is lossless, but making a PNG much smaller usually means reducing its colours, which is lossy. PicoDiet measures that loss and only keeps results that look the same at your chosen score. If no smaller version is good enough, you keep the original file.
Does PicoDiet keep transparency?
Yes. Transparent and semi-transparent pixels are kept, so icons and cut-outs still sit cleanly on any background.
Why did my PNG barely shrink?
It was probably already optimized, or it is a photo that needs full colour to keep its score. For photos, choose Auto to convert them to JPEG, which is usually far smaller.
What is the difference from TinyPNG?
Both reduce colours. PicoDiet picks the number of colours per image by measuring how it looks, shows you the score and where the image changed, and takes 30 images per batch.
Is there a size limit?
Each image can be up to 25 megapixels and 30 MB, up to 30 images at once.
Are my images private?
Yes. Images are uploaded over an encrypted connection to the nearest of our servers, optimized, and deleted within 3 minutes after you finish. They are never shared, sold or used for training, and there is no account to sign up for. Details are in the privacy policy.