Metacognition refers to a capacity to reflect on and control other cognitive processes, commonly quantified as the extent to which confidence tracks objective performance. There is conflicting evidence about how metacognition changes across the lifespan and it is unknown whether “local” metacognition (monitoring of individual judgments) and “global” metacognition (estimates of self-ability) change. Additionally, the degree to which metacognition generalises across cognitive domains may itself change over time due to increased experience with one’s own abilities. Using a gamified metacognitive task we measured local and global metacognition during performance-controlled memory and visual perception tasks in an age-stratified sample of 304 healthy volunteers (18-83 years; N=50 in each of 6 age groups). We calculated both local and global metrics of metacognition and charted domain-generality with age. Task performance was stable with age. Global self-performance estimates and local metacognitive bias decreased with age, indicating overall lower confidence. Local metacognitive efficiency was unrelated to age and remained correlated across the two cognitive domains. A stability of local metacognition indicates distinct mechanisms contributing to local and global metacognition. Our study provides both a profile of local and global metacognition across the lifespan and a benchmark against which disease-related changes in metacognition can be compared.