Merge images

The order they have in the list, left to right and top to bottom. Every row has two buttons to move it one place up or down, and the row itself tells you which position it holds, so you can reorder without dragging anything. The preview redraws the moment the order changes, and what you see there is the exact layout of the file you will get.

No, and that is a decision rather than a limitation. Every cell is the same size — the size of the largest image in your list — and each photo is fitted inside its own cell whole, losing nothing at the edges. If a photo is portrait and the cell is square, the background colour you picked shows at the sides. Cropping without warning is the quickest way to take half of someone off the picture; if cropping is what you want, the crop tool is right next door.

Three things: the spacing between images, the border around the whole thing, and the gap in the last row when your images do not fill the grid. It also fills the transparent areas of a PNG, which is what stops them turning black when you save as JPG. What it does not touch is the background of your photos — that lives in the pixels of the image, and nothing here changes those.

Up to thirty. The limit is not commercial: composing them means holding all of them uncompressed in memory at once, and past that number the tab runs out of memory and closes on you with no explanation. Size you do not need to think about — if the composition comes out enormous, the whole thing is scaled down proportionally, keeping every ratio, until it fits inside what browsers will encode without failing. In practice that is around 8,000 pixels a side and around 40 megapixels in total, and the tool does the scaling for you.

No. The layout is worked out and drawn inside your browser. You can confirm it with the Network tab of your developer tools open, or by disconnecting the internet once the page has loaded: the tool keeps working exactly the same.