Rendertools is a Blender addon by Picto Filmo that brings together several tools aimed at improving productivity in rendering output. Rather than a single function, it bundles related utilities that you enable individually from the addon preferences by clicking on the diamonds. It works with both the Cycles and Eevee render engines.
A recent addition in version 1.0.6 is an Export Video to GIF feature, which exports video to GIF format. This export relies on FFMPEG being installed on your system, and the developer provides setup instructions for Windows and macOS. The developer states the GIF export works on Linux, while support on Windows and macOS is noted as less certain.
The addon targets Blender versions 4.5 through 5.1 and is released under the GPL license. Documentation is included, and a demo video is available. For current details and licensing, check the developer's page.