The article discusses the limitations of the Louvain algorithm in community detection and introduces the Leiden algorithm as an improvement. The Louvain algorithm, while widely used, can produce arbitrarily badly connected communities, even leading to disconnected communities in some cases. This issue is not just a theoretical concern but is observed in practice, with up to 25% of communities being badly connected and up to 16% being disconnected. The Leiden algorithm addresses this problem by guaranteeing that all communities are connected and providing stronger guarantees about the quality of the partitions. It also converges to a partition where all subsets of communities are locally optimally assigned. The Leiden algorithm is faster than the Louvain algorithm and performs better in terms of partition quality. The article presents experimental results showing that the Leiden algorithm outperforms the Louvain algorithm on both benchmark and real-world networks, with significant improvements in speed and quality. The Leiden algorithm is also more robust, as it avoids the issue of arbitrarily badly connected communities. The paper concludes that the Leiden algorithm is strongly preferable to the Louvain algorithm for community detection in complex networks.The article discusses the limitations of the Louvain algorithm in community detection and introduces the Leiden algorithm as an improvement. The Louvain algorithm, while widely used, can produce arbitrarily badly connected communities, even leading to disconnected communities in some cases. This issue is not just a theoretical concern but is observed in practice, with up to 25% of communities being badly connected and up to 16% being disconnected. The Leiden algorithm addresses this problem by guaranteeing that all communities are connected and providing stronger guarantees about the quality of the partitions. It also converges to a partition where all subsets of communities are locally optimally assigned. The Leiden algorithm is faster than the Louvain algorithm and performs better in terms of partition quality. The article presents experimental results showing that the Leiden algorithm outperforms the Louvain algorithm on both benchmark and real-world networks, with significant improvements in speed and quality. The Leiden algorithm is also more robust, as it avoids the issue of arbitrarily badly connected communities. The paper concludes that the Leiden algorithm is strongly preferable to the Louvain algorithm for community detection in complex networks.