Performance and stability of anaerobic digestion are affected by several environmental factors including pH, temperature and the presence of inhibitors. The resilience of anaerobic microbes to chemical inhibitors is an important feature of anaerobic digesters and is commonly expressed as the inhibitor concentration at which the microbial activity is halved (KI50). Ammonia nitrogen is a common inhibitor in anaerobic digesters, especially in the digestion of animal manure. Microbial acclimation has been shown to enhance resilience to ammonia nitrogen beyond 3000 mg NH4-N·L-1, leading to the question of whether the microbial community composition can be a predictor for inhibition resilience. In this study, inhibition resilience to ammonia, microbial communities, as well as operating conditions of 10 full-scale and 3 pilot-scale anaerobic digesters were characterized, examining links between resilience to ammonia inhibition and microbial community composition in the digesters. The inocula under study were diverse in terms of substrate type, digester configuration, and operating conditions. The results showed that microbial composition was not significantly correlated with resilience as expressed as KI50. However, the microbial communities (either overall, bacterial or archaeal community) and the speed of onset of inhibition were significantly influenced by substrate type (dominant predictor) and temperature, and the archaeal community was significantly correlated with the specific methanogen activity (p=0.008, negative correlation coefficient). The later could be due to the emergence of a diverse community consisting mainly Methanosaeta and Methanobacteria. Free ammonia nitrogen was also significantly correlated to the archaeal community, but only when tested separately to substrate type and temperature, indicating that it is a predictor rather than a primary factor for the archaeal community. Overall, microbial community composition does not seem strongly linked with ammonia inhibition resilience. In fact, the degree of variation of resistance seems to be limited compared with literature experience, despite a wide range of reactor type and in-reactor conditions.