PNG to WebP, in your browser

Why convert PNG to WebP?

WebP files are typically 25-35% smaller than equivalent PNGs at visually identical quality. For a website serving tens of thousands of image requests a day, that adds up to real bandwidth savings and faster page loads. For a developer building a static site, WebP shrinks your bundle without forcing you to give up alpha transparency.

PNG remains a fine archival and editing format, but for delivery to browsers, WebP usually wins. Every modern browser supports it. If you need PNG fallbacks for legacy clients, ship both with a <picture> element.

How this converter works

Your PNG is decoded by the browser via createImageBitmap. The decoded ImageBitmap is drawn onto an OffscreenCanvas inside a dedicated Web Worker. We then call convertToBlob with type "image/webp" and your chosen quality (default 80 out of 100). The result is a Blob in worker memory; we hand it back to the page for download.

No WebAssembly. The browser already ships a WebP encoder, and using it keeps the bundle small and the conversion fast. This converter's manifest declares an empty wasmModules array, which you can verify at /manifests/png-to-webp.json.

Picking a quality

WebP quality is a number from 1 to 100. 80 is a sensible default: visually indistinguishable from the source for most photos and screenshots, with significant size savings. 90 keeps more detail at the cost of larger files. Below 60, you start to see WebP's blocking artifacts in flat areas.

For graphics with sharp edges and flat colors (logos, UI screenshots, line art), WebP's lossy mode can blur edges. Consider using a higher quality or sticking with PNG for that kind of content. WebP also supports a true lossless mode; we will expose that as a toggle in a future release.

What about transparency?

Both PNG and WebP support full alpha channels. We preserve them. If your PNG has transparent pixels, the resulting WebP will too. The browser's WebP encoder handles alpha correctly; no extra configuration needed.

Privacy, audited by you

Drop a PNG. Open DevTools, switch to Network. The only requests you will see are for our static assets and the manifest. Nothing about your image leaves the page. The conversion happens in a Web Worker that has no network access by design (CSP enforces this).

If you have any doubt, the source code for this converter is online. The relevant file is small enough to read in a single sitting. Verify, do not trust.