What does it mean to overlay images?
Overlaying images means putting one picture on top of another so both show through in the same frame — the top picture can sit at full strength or be made see-through. It is different from merging photos side by side: an overlay composes the pictures into one shared canvas, which is how watermarks, logos, badges, and double-exposure effects are made.
How do I put one image on top of another?
Add your background picture first — it becomes the base and sets the canvas size. Then add the second picture, which lands in the middle of the canvas as a top layer. Drag it where you want it, resize it with the scroll wheel or the scale slider, lower its opacity if it should show through, and download. The result is one flattened image file.
What does opacity mean, and what does 50% transparency look like?
Opacity is how solid a layer appears. At 100% the layer fully covers whatever is beneath it; at 50% the two pictures blend evenly, like a ghost; at 0% the layer disappears entirely. A watermark usually sits between 20% and 40% so it is readable but does not hide the photo under it.
Should I export the overlay as PNG or JPG?
PNG if anything in the result should stay transparent — for example a base PNG with a transparent background, or an overlay exported without a background at all. JPG does not support transparency, so this tool composites JPG exports onto white first. For opaque photos either format works; PNG is lossless while JPG uses adjustable compression.
Can I use this to put a logo or watermark on my photos?
Yes, that is the most common use. Add the photo as the base, add the logo as the top layer, drag it into a corner, and set its opacity to around 20–40% so it reads without covering the picture. Export as PNG to keep everything crisp. For a whole batch, do the photos one at a time — the tool keeps your last layer settings during a session.
How many images can I stack on top of each other?
Up to ten layers in total, including the base. Each layer keeps its own position, scale, and opacity, and you can reorder them at any time, so a photo with a logo, a badge, and a caption graphic on top is well within range.
Can I change which image is on top after layering?
Yes. Select a layer in the panel and use the up or down arrows to move it forward or backward in the stack. The base image always stays at the bottom because it defines the canvas size, but every layer above it can be reordered freely.
Are my images uploaded to a server?
No. The overlay is composited directly in your browser with the HTML5 Canvas API, and the exported file is generated on your own device. Nothing is sent anywhere, nothing is stored, and closing the tab discards everything.