PNG Compressor

Why compress or convert a PNG?

PNG is everywhere — it’s the default for screenshots, the go-to for logos and icons, and the standard for any graphic that needs a transparent background. The catch is that PNG files are often bigger than they need to be. Image editors and screenshot tools save generous, unoptimized files with extra metadata, suboptimal compression settings, and color data they don’t need. Optimizing strips that waste away so pages load faster, attachments send quicker, and storage goes further.

Because this tool runs entirely on your device, it’s also the private way to do it. Traditional online optimizers upload your images to a remote server, process them there, and send them back. Here, each PNG is read into memory, rewritten with a WebAssembly build of OxiPNG, and handed straight back to you — your files never touch a network, which matters when a screenshot or design asset contains sensitive information.

Lossless optimization vs. lossy conversion

PNG is a lossless format: it reproduces every pixel exactly, with no compression artifacts and full support for transparency. That fidelity is the whole point of PNG, but it also limits how small a PNG can get. OxiPNG keeps your image pixel-perfect — it only finds a more efficient way to store the same data by reducing the color palette where possible, choosing better filters, and dropping needless chunks. Be honest about the math: lossless savings are modest, typically 5–30%, and an already-optimized PNG may barely shrink at all.

When you need a dramatic reduction, the answer isn’t a better PNG — it’s a different format. Converting a PNG to WebP or AVIFapplies lossy compression that can cut file size by 60–90% while still supporting transparency. The trade-off is that lossy conversion can introduce subtle changes, so it’s ideal for photographs and complex images, while lossless PNG stays best for sharp-edged graphics where every pixel matters. This tool lets you choose: keep PNG for fidelity, or switch the output to WebP for size.

What is a PNG, and when should you use it?

PNG (Portable Network Graphics) was created as a patent-free, lossless replacement for GIF. It uses DEFLATE compression together with per-row prediction filters, and supports a full 8-bit alpha channel for smooth transparency. That makes it excellent for logos, icons, screenshots, line art, charts, and any image with sharp edges, flat color, or text — content that lossy formats blur or surround with halos. You can read the technical details on MDN’s image format reference.

PNG is the wrong choice for photographs. Because it never discards detail, a continuous-tone photo becomes an enormous PNG — often many times larger than the same image as a JPEGor WebP. If you’ve been saving photos as PNG, that single habit is probably your biggest source of bloat. Reach for PNG when you need crisp edges or transparency, and reach for a lossy format when you have a photo. Not sure which to use? Our image converter lets you try both and compare the results side by side.

Tips for the best results

• Match the optimization level to the job. Use “Fast” for a quick pass on many files, and “Max” when squeezing every last byte from a single hero image is worth the extra processing time.
• Resize before you optimize. A 4K screenshot shown at 800px wide is mostly wasted pixels. Use the built-in resize option for a far bigger saving than lossless optimization can ever deliver on its own.
• Convert photos, don’t fight them.If a “PNG” is really a photo, switch the output to WebP instead of expecting lossless optimization to work miracles.
• Keep PNG for transparency. When you need a transparent background and broad compatibility, lossless PNG is the safe pick — and OxiPNG keeps that alpha channel pixel-perfect.