Check Image Transparency Online
Detect transparency in any image - counts fully opaque, fully transparent, and semi-transparent pixels with percentages. Free, client-side.
Drop any image in to see exactly how many pixels are fully opaque, fully transparent, or partially translucent — checkerboard preview included.
Click to upload or drag and drop
PNG · WebP · GIF · JPG — analysis runs locally, file stays on your device
Details
How to Use Check Image Transparency Online
- Drop an image on the upload zone, or click to pick from the file picker. PNG, WebP, GIF, and JPG all work - the extension does not matter.
- Read the verdict: green means the image contains at least one transparent or semi-transparent pixel; amber means every single pixel is alpha 255 (fully opaque).
- Inspect the preview - a checkerboard pattern behind the image highlights transparent and semi-transparent areas so you can see them at a glance.
- Scan the details card: fully-opaque / fully-transparent / partially-transparent pixel counts with percentages, plus the average and minimum alpha across every pixel.
- Press
Ctrl+Enter(⌘+Enteron Mac) to re-run the check on the last image - handy if you swap the file on disk. - Copy the report to your clipboard or Download a timestamped `.txt` file that embeds the original filename for archiving.
Frequently asked questions
Is my image uploaded anywhere?
No. The entire analysis runs in your browser using the HTML5 canvas API. The file is read locally, never sent to a server.
How does the tool detect transparency?
It decodes your image, draws it onto a canvas, then walks every pixel’s alpha byte. Pixels with alpha 255 are fully opaque; alpha 0 is fully transparent; anything in between is semi-transparent.
Which image formats support transparency?
PNG, WebP, GIF, and a handful of others. JPEG does not – every JPEG pixel is opaque by definition, so the tool will always report 100% opaque for JPEGs.
Why does my PNG show 100% opaque?
Not every PNG has transparency. If the image was flattened against a solid background before export, or saved without an alpha channel, every pixel will be alpha 255. The tool correctly reports it as opaque.
What does “partially transparent” mean?
It is any pixel whose alpha is strictly between 0 and 255 – so semi-translucent. A soft drop shadow, anti-aliased edge, or foggy overlay all create partially transparent pixels.
Can it handle animated images?
Only the first frame. Canvas decodes animated GIF and WebP as a single still image, so the tool reports on that frame and ignores later ones.
What’s “average alpha”?
The mean of every pixel’s alpha byte (0-255). A fully opaque image averages 255; a half-transparent overlay averages around 128; a fully invisible image averages 0.
What’s “minimum alpha”?
The lowest alpha value found in the image. If it is 255, every pixel is fully opaque. If it is anything less than 255 the image has transparency somewhere – useful when you want a yes/no answer at a glance.
Is there a size limit?
No hard limit, but images over 8000×8000 pixels trigger a warning because memory caps vary by browser. Typical photos scan in well under 100 ms.
Does it work offline?
After the page loads, yes. HTML, CSS, and JS are self-contained, so you can disconnect Wi-Fi and keep checking images.