Change WebP Opacity
Change WebP Opacity with a live slider, scale or overwrite the alpha channel, export as WebP or PNG. Free, client-side, instant, secure.
Fade or overwrite the alpha channel of a WebP image with a live slider — preserves source transparency by default.
Click to upload or drag and drop
WebP · PNG · JPG — stays on your device
How to Use Change WebP Opacity
- Drop or pick a WebP (or PNG/JPG) into the upload area. The original preview appears as soon as the file decodes.
- Drag the opacity slider from 0% (fully transparent) to 100% (fully opaque). The percent badge updates live and the preview re-renders with a 100 ms throttle.
- Pick a mode: "Scale existing alpha" fades the image while keeping already-transparent pixels transparent. "Set absolute alpha" overwrites every pixel's alpha to the chosen value, even previously-transparent ones.
- Choose the output format: WebP with an adjustable quality slider (1-100) or PNG (lossless - the quality slider hides).
- Watch the checkerboard behind the preview - it highlights transparent areas so you can see alpha changes without loading the image into a photo editor.
- Press
Applyor hitCtrl+Enter(⌘+Enteron Mac) if you disabled live updates. Stats show average alpha before and after plus the count of fully-transparent pixels. - Copy to clipboard (Chrome/Edge support real image copy; other browsers fall back to a data URL) or Download a timestamped file with the correct extension.
Frequently asked questions
Is my image uploaded anywhere?
No. Decoding, alpha adjustment, and re-encoding all happen in your browser. The file never leaves your device – there is no fetch or XHR for the image.
What’s the difference between Scale and Set alpha?
Scale multiplies each pixel’s existing alpha by your chosen percent, so a transparent PNG stays transparent where it was. Set overwrites every pixel’s alpha to the same value, which turns previously-transparent areas semi-visible.
Why does my image look fully opaque before I change anything?
JPEG sources have no alpha channel, so every pixel starts at 100% alpha. The stats line shows the average alpha before and after, so you can verify what the tool read from the file.
Can I export without re-encoding?
No browser API can read-then-rewrite WebP without re-encoding, so the tool has to encode fresh. Choose PNG output for a lossless result, or set WebP quality to 100 for the closest round-trip.
Does opacity 0% save a useful image?
It saves a fully-transparent image of the source dimensions – useful as an invisible placeholder but not much else. The stats line will report 100% fully-transparent pixels to confirm.
Does the tool support animated WebP?
No. Canvas decodes animated WebP as a single still frame, and the output will be a static image. Use a dedicated video or GIF tool for animation.
Why are there two file-size numbers in the stats?
The first is your source file’s byte size, the second is the re-encoded output. Comparing them tells you whether the tool expanded or shrunk the file at the current settings.
Is there a size limit?
No hard limit, but very large images (over 8000×8000 pixels) trigger a warning because memory caps vary by browser. Typical photos process in under 100 ms.
Why checkerboard behind the preview?
The checkerboard pattern is the standard way to visualise transparency. Where you see the grid through the image, those pixels are partially or fully transparent.
Does it work offline?
After the page loads, yes. HTML, CSS, and JS are self-contained, so you can disconnect Wi-Fi and keep adjusting opacity.