Simultaneous localization and mapping (SLAM) is central to the foundation of robotic exploration. Over the decades, numerous advancements have been made in the field of SLAM. Currently, most of the applications based on SLAM are implemented using a single robot. In practical applications like search and rescue operations, there is a need to implement SLAM at a multi-robot level. This paper conducts a review on SLAM at a multi-robot level. © 2022, The Author(s), under exclusive license to Springer Nature Singapore Pte Ltd.