Social networking is a digital phenomenon embraced by billions worldwide. Use of online social platforms has the potential to generate a number of benefits including to well‐being from enhanced social connectedness and social capital accumulation, but is also associated with several negative behaviours and impacts. Employing a life‐course perspective, this paper explores social networking use and its relationship with measures of subjective well‐being. Large‐scale UK panel data from wave 3 (2011–12) and 6 (2014–15) of Understanding Society reveals that social network users are on average younger, aged under 25, but that rising use is reported across the life‐course including into old age. Probit, multinomial logistic, and ANCOVA and change‐score estimations reveal that membership, and greater use, of social networks is associated with higher levels of overall life satisfaction. However, heavy use of social networking sites has negative impacts, reflected in reductions in subjective well‐being. Socio‐economic disadvantage may drive these impacts among young (in education), unemployed and economically inactive heavy SNS users.