Combine multiple GIFs together

Make a GIF, where two or more GIFs play simultaneously, at the same time.

We will see how to do it in Photopea.com. First, learn how to add a GIF into a still image.

Open the main background image (or make an empty image with File - New). Now, open two or more GIFs (with File - Open) and duplicate their layers into the main image. You can move them, resize, rotate etc. If you export it now, animations will paly one after another (not simultaneously).

Now, simply press Layer - Animation - Merge. The structure will change as illustrated below.

Now, just press File - Export as - GIF, Save, and you are done :)

Example

Here, we put two GIFs on the image of a beach. The first GIF (hamsters) is enlarged.

Hamsters: 5.6 KB, Mario: 132 KB, Beach + Hamsters + Mario: 151 KB.