Is my PNG uploaded to compress it?

No. The conversion runs in your browser using WebAssembly and canvas APIs, so the image data never leaves your device. There is no upload endpoint in this application at all — you can watch the network tab while you convert.

Is PNG compression lossless here?

Yes. OxiPNG only re-encodes the same pixel data more efficiently. Decode the input and the output and they are identical.

Why did my PNG barely get smaller?

It was probably already well optimised. There is no more redundancy to remove without discarding pixels, which lossless compression will not do.

How do I make a PNG much smaller?

Resize it if it is larger than it needs to be, or convert it to WebP, which keeps transparency and compresses far harder than PNG can.

Does transparency survive?

Yes, completely. The alpha channel is preserved exactly.

Compress a PNG

Make a PNG smaller without changing a single pixel. The optimiser runs on your device and the file is never uploaded.

Free
No signup
No watermark
Files stay on your device

Drop an image hereor browseJPEG • PNG • WebP • AVIF where supported

Processed locally

Your image never leaves your computer.

How to compress a png

1
Choose your PNG
Drop the PNG onto the page, or browse for it.
2
PNG is already selected
There is no quality slider, because PNG compression here is lossless.
3
Compress and download
Press the button and compare the sizes before saving.

The honest truth about “PNG quality” sliders

Many tools show a quality slider for PNG. For a plain browser canvas export that slider does nothing at all — the browser ignores it, because PNG has no lossy quality setting.

Rather than pretend, this tool runs OxiPNG, a real PNG optimiser, over the output. It re-tries filtering and compression strategies to find a smaller encoding of exactly the same pixels. The result is byte-for-byte identical when decoded.

How much can you expect to save?

Exports from design tools often lose 10–30%, because they optimise for export speed rather than size.
Files already run through an optimiser may barely move — that is a good sign, not a failure.
If you need a dramatic reduction and the destination is the web, converting to WebP will beat any lossless PNG optimiser by a wide margin.

Frequently asked questions

Is my PNG uploaded to compress it?: No. The conversion runs in your browser using WebAssembly and canvas APIs, so the image data never leaves your device. There is no upload endpoint in this application at all — you can watch the network tab while you convert.
Is PNG compression lossless here?: Yes. OxiPNG only re-encodes the same pixel data more efficiently. Decode the input and the output and they are identical.
Why did my PNG barely get smaller?: It was probably already well optimised. There is no more redundancy to remove without discarding pixels, which lossless compression will not do.
How do I make a PNG much smaller?: Resize it if it is larger than it needs to be, or convert it to WebP, which keeps transparency and compresses far harder than PNG can.
Does transparency survive?: Yes, completely. The alpha channel is preserved exactly.