PNG Optimizer
Shrink PNG files without changing how they look. Choose lossless optimization to recompress the exact same pixels more efficiently, or reduce the image to a palette of 256 colours or fewer – usually invisible for screenshots, logos and illustrations and often 50–80% smaller. Dithering keeps gradients smooth, transparency is kept, and you can compare before and after.
- Files stay on your device
- No sign-up
- Free to use
How to use PNG Optimizer
- Drop PNG files onto the page.
- Choose lossless or a colour count, and dithering.
- Optionally limit the maximum size.
- Optimize and download, one by one or as ZIP.
PNG Optimizer features
Lossless mode
Same pixels, better compression.
Palette reduction
256 down to 16 colours.
Dithering
Smooth gradients with few colours.
Transparency kept
Alpha channel preserved.
Never larger
Keeps the original if it cannot be improved.
Private
Converted in your browser; nothing is uploaded.
When to use PNG Optimizer
- Faster websites with lighter PNG graphics.
- Screenshots for documentation and support.
- Icons and UI assets for apps.
- Meeting upload size limits.
PNG Optimizer FAQ
What is the difference between lossless and colour reduction?
Lossless keeps every pixel exactly and only finds a more compact encoding. Colour reduction replaces millions of possible colours with a palette, which allows the much smaller 8-bit indexed PNG format.
Will reducing to 256 colours be visible?
Rarely for graphics, screenshots and illustrations. Photos with smooth skies may show slight banding, which dithering hides.
Why is my photo PNG still large?
PNG is lossless and not efficient for photos. Use the JPG or WebP optimizer for photographs.
Is the result still a normal PNG?
Yes. Indexed PNGs are part of the PNG standard and open everywhere.
Are my files uploaded?
No. Everything happens in your browser.
How PNG optimization works
PNG compresses images losslessly with DEFLATE, after applying a filter to each row that makes the data more predictable. How well this works depends on the encoder’s choices of filters and compression effort, and many programs choose quickly rather than well. Re-encoding with a thorough encoder often reduces the size without any change to the pixels.
The bigger saving comes from the colour model. A typical PNG stores 24 or 32 bits per pixel. An indexed PNG stores one byte per pixel that points into a palette of up to 256 colours. For graphics with a limited number of colours – logos, charts, screenshots, illustrations – this cuts the raw data by three or four times before compression even starts.
Choosing the palette is the art. The optimizer analyses the image with a median-cut algorithm, which repeatedly splits the colour space where the image’s colours are most spread out, so the palette represents the actual image rather than a fixed set. Floyd–Steinberg dithering then distributes the rounding errors to neighbouring pixels, so gradients stay smooth.
If an optimized file is not smaller than the original, the original is kept. The before-and-after slider shows the result at full detail.
All processing happens on your device.