Is the WebP alpha viewer free?
Yes. The WebP Alpha Channel Viewer is completely free and runs entirely in your browser with no sign-up.
Does it upload my WebP file?
No. Alpha inspection and PNG export happen locally in your browser, so your WebP file stays on your device and is never uploaded.
Can I inspect animated WebP transparency frame by frame?
Yes. Animated WebP defaults to the first frame and then lets you switch between frames to inspect the alpha of each one.
Can I export the alpha result?
Yes. The current alpha or alpha-mask view can be downloaded as a PNG file directly from the browser.
Does it work on mobile?
Yes. The viewer runs in the browser, so you can inspect WebP alpha on a phone or tablet with the file staying on your device.
Why does my WebP look transparent in one app and white in another?
Usually because the alpha is there but the consumer is compositing it onto white without telling you. Load the file here and check the alpha view: if it shows black regions, the transparency is genuinely in the file and the other app is flattening it. If the alpha view is entirely white, the file has no usable transparency and the app is showing you the truth.
What is the difference between the alpha view and the alpha mask?
The alpha view keeps every intermediate value, so a feathered edge appears as a grey gradient. The alpha mask collapses everything to black or white using a threshold of 16, so the same feathered edge becomes a hard line. Looking at both tells you whether your cutout has real soft edges or is effectively a hard-edged shape with noise around it.
Can I inspect a specific frame of an animated WebP?
Yes. Animated files are detected from the RIFF header and decoded into individual frames, and the frame selector lets you view any one of them in any channel. That is how you catch the frame in a loop that has broken alpha, which is otherwise almost impossible to see at animation speed.
Can I use the exported alpha as a mask in another tool?
You can, with a caveat. The export is a PNG of the grayscale rendering, so it is a correct grayscale mask that you can paste into a design tool as a luminance mask. It is not the original alpha channel data reattached to the original RGB, so it will not round-trip back into a WebP as-is.
Does the WebP get uploaded to be inspected?
No. The file is decoded in the page and every channel view is rendered on your device, so an unreleased asset or a client's artwork stays local. The only network call is a credit counter carrying the tool name.