Does WebP support transparency in lossy mode?

Yes. WebP supports an alpha channel in both its lossless and lossy modes. The alpha channel itself is always lossless, even when the color data is compressed lossily.

Is a transparent WebP always smaller than a transparent PNG?

For lossless images, WebP is about 26% smaller than PNG. For lossy images with transparency, WebP can be much smaller than PNG, especially for photographic cut outs.

Can I convert a PNG with transparency to WebP without losing the alpha channel?

Yes. You can convert PNG to WebP transparent using tools that preserve the alpha channel. The resulting WebP will have the same transparent areas.

Should I delete my PNG after converting to WebP?

No. Keep the original PNG as a master and publish WebP copies. PNG is more widely supported in older software and email clients.

Transparent WebP vs PNG: Which Is Smaller?

For images that need an alpha channel, WebP beats PNG on file size almost every time. Google reports that a WebP using reversible compression is about 26% smaller than the equivalent PNG. For photographic cut-outs, a lossy WebP with an alpha layer can shrink the file dramatically. The crisp edge stays. That matters for logos, stickers, and any asset where the silhouette must be perfect.

How WebP Handles an Alpha Channel

WebP supports an alpha channel in both its reversible and lossy modes. You can store see-through regions regardless of which compression path you pick. The alpha data itself is always stored without loss, even when the colour information is compressed aggressively. For graphics with hard edges or text, this is the key advantage: the boundary stays sharp while the rest of the image shrinks.

PNG Alpha is Always Reversible

PNG handles see-through areas with a single, lossless alpha channel. Every pixel’s opacity value is stored exactly as encoded. That makes PNG a reliable master format for any asset that requires pixel-perfect edges. The trade-off is file size. PNG cannot apply lossy compression to the colour data while preserving the alpha, so images with many colours or gradients stay large.

Key differences:

WebP: lossy or reversible colour, always lossless alpha.
PNG: lossless colour and lossless alpha.
WebP can be 26% smaller than PNG for reversible images; even smaller for lossy files with an alpha channel.

When WebP Wins for Images with an Alpha Channel

Logos and Stickers with Hard Edges

Logos use a small number of flat colours and a sharp see-through boundary. A reversible WebP will be smaller than a PNG of the same logo. For logos with fine detail, lossy WebP with alpha can reduce the file further without visible degradation because the alpha edge remains lossless.

Photographic Cut-Outs

A photo of a person or object on a see-through background is where lossy WebP with alpha excels. The colour data compresses heavily. The alpha channel stays intact. PNG cannot do this. It must store all colour data without loss, which produces a larger file.

Stickers and Icons

Stickers and icons mix flat colour, gradients, and soft edges. A reversible WebP beats PNG on size. If the sticker uses many colours, lossy WebP at a high quality setting shrinks the file further while the edge stays perfect.

Limitations of WebP for Images with an Alpha Channel

WebP is not the right choice everywhere. All current major browsers display it. Some older desktop software and email clients do not. Sending a see-through image to someone on older software? Use PNG. WebP’s maximum dimensions are 16383 x 16383 pixels. That is larger than most assets need, but check the limit if you work with extremely large files.

Lossy WebP with alpha can introduce compression artefacts in the colour areas. For images with text or fine lines, use reversible WebP or PNG to avoid blurring.

How to Decide Between WebP and PNG

Web-only? Choose WebP for smaller file sizes.
Text or fine lines? Use reversible WebP or PNG to preserve sharpness.
Photographic cut-out? Lossy WebP with alpha gives the best size reduction.
Email or old software? Stick with PNG.
Keep the original PNG as a master. Publish WebP copies for web delivery.

Practical Workflow for See-Through Images

Start with a PNG master that holds the alpha you need. From that master, create a WebP copy. For logos and icons, use reversible WebP compression. For photos with an alpha channel, try lossy WebP at a high quality setting. Compare the result to the original. If the file is much smaller and the quality holds, serve the WebP version on your site.

Convert PNG to WebP with an alpha channel using a tool like tinyimgcompress.com. Upload your PNG. It outputs a WebP with the same see-through data.

Transparent WebP vs PNG at a Glance

For images with an alpha channel, WebP is smaller than PNG. Reversible WebP is about 26% smaller. Lossy WebP with alpha shrinks photographic cut-outs even further. PNG remains the safer choice for compatibility with older software and email. Keep a PNG master. Serve WebP copies to the web.