Why PNG files get so large
PNG is a lossless format, which means it records every single pixel exactly as it was created and never throws anything away. That is precisely why designers reach for it: a logo stays razor-sharp, a screenshot keeps its crisp text, and a cut-out product photo carries a genuine transparent background. The downside is weight. Because PNG must describe every pixel faithfully, a colourful or photographic image can balloon into several megabytes, far heavier than it needs to be for a web page.
The good news is that you rarely have to accept those big files. To shrink a PNG properly you want a format that keeps PNG's strengths (perfect edges and transparency) but stores them far more efficiently. That is exactly what our tool does when you open the compressor and drop your images in.
Lossless WebP usually beats PNG, and keeps transparency
The single most effective way to compress a PNG is to convert it to lossless WebP. Lossless WebP keeps every pixel identical to the original, transparency and all, yet its encoder is much smarter than PNG's, so the resulting file is typically a good deal smaller with no visible change whatsoever. For logos, icons, UI screenshots and line art, this is almost always the right move: you lose nothing and gain a lighter file. If you want the full picture of how the format works, our guide to converting images to WebP walks through it.
For every image, the compressor produces both a lossless copy and a lossy copy and shows you the file size of each, so you can pick with confidence rather than guessing.
PNG vs lossless WebP vs lossy WebP: a sample
The table below shows a representative screenshot-style PNG and how it compares across the three options. Your own results will vary with the image, but the pattern is consistent.
| Version | Example file size | Quality | Transparency kept |
|---|---|---|---|
| Original PNG | 1.8 MB | Pixel-perfect | Yes |
| Lossless WebP | 0.9 MB | Pixel-perfect (identical) | Yes |
| Lossy WebP (q80) | 0.3 MB | Visually indistinguishable | Yes |
Lossless WebP roughly halved the file with no change at all, whilst lossy WebP cut it by more than 80% for cases where a tiny, imperceptible change is acceptable.
When lossy WebP is fine for a PNG
Not every PNG needs to stay perfectly lossless. If your PNG is really a photograph that happened to be saved as PNG (a screenshot of a photo, a graphic with soft gradients, or a banner image), then lossy WebP at quality 80 will look identical to the eye whilst being dramatically smaller. Reserve strict lossless output for graphics where absolute pixel fidelity matters, such as small icons, pixel art, or diagrams with fine one-pixel lines. For a deeper comparison of the trade-offs, see our WebP vs JPG vs PNG breakdown.
Handling transparency and alpha
Transparency is where PNG earns its keep, and it is preserved throughout. Both the lossless and lossy WebP outputs retain the full alpha channel, so a logo on a transparent background stays transparent: there is no white rectangle stamped behind it, and semi-transparent edges (the soft anti-aliasing around curved shapes) remain smooth. This makes the tool safe for exactly the assets people worry about most: brand marks, favicons, cut-out products and overlay graphics.
Screenshots, websites and Core Web Vitals
Screenshots are one of the biggest sources of oversized PNGs. A single full-page capture can weigh more than an entire article's worth of text, and dropping several onto a page slows it noticeably. Because page speed feeds directly into Google's Core Web Vitals, and therefore into rankings and bounce rates, trimming those PNGs is one of the easiest performance wins available. Convert them to WebP, and if the screenshots are large you can also resize them: the compressor offers four sizes (Original, −25%, −50% and −75%) with the aspect ratio preserved and high-quality resampling.
Compress lots of PNGs at once
Working through a folder of assets is quick. Drop every PNG in together, let the tool compress the whole batch, review the before-and-after sizes, and download the lot as a single ZIP. It all runs on your own device using the real libwebp encoder in WebAssembly, so your files are never uploaded and nothing is queued on a server. The compressor is free forever, needs no account, adds no watermark, works on desktop and mobile, and is made in the UK, with more output options, including AVIF export, on the roadmap.
Frequently asked questions
Can I compress a PNG without losing quality?
Yes. Converting a PNG to lossless WebP keeps every pixel identical, transparency included, whilst usually producing a noticeably smaller file. Nothing is discarded, so the image stays pixel-perfect, ideal for logos, icons and screenshots.
Will compressing a PNG keep the transparent background?
Yes. Both the lossless and lossy WebP outputs preserve the alpha channel, so transparent backgrounds remain transparent. No white box is added behind your logo or cut-out image, and soft edges stay smooth.
Why is my PNG so large?
Because PNG is lossless, it stores every pixel exactly, perfect for sharp graphics but heavy for photographs. Converting to WebP keeps the qualities you actually want whilst removing the storage overhead that PNG cannot avoid.