A free app for Windows, by ThunderSoft.

Joining multiple GIFs into one video file is an important task, especially if you want to create a long-lasting video clip from animated images. The resulting video would be of good quality and be able to be played back at any time. This is because a video file is composed of multiple frames, and each frame must be loaded from the device memory. The process of loading an image for a frame can take time, so you will need to find a way to make it faster.

If you are looking for a tool to make GIFs joinable, then this application is perfect for you.

Best software to join animated gif files without any quality loss.

Free GIF Joiner is a handy tool to join animated gif files. Provide gif file frame by frame preview, use every frame from original image to make output gif files, with fast speed and no quality loss. This software also supports join gif file with static image files(such as jpg, png, bmp files).

Key features
Supports join with gif, jpg, png and bmp files.
Provide gif file frame by frame preview.
Fast speed and no quality loss(gif file only).
Keep original transparent effect(gif file only).
Allow specify image stay time(static image file only).
Allow change gif speed.
Allow config replay times.