The smartphone has grown from non-existent to ubiquitous in the last 20 years. Learners can use a plethora of apps to help their language development, whether designed for such purposes or not, but may not engage in a process of reflection on what activity best suits their needs. Trying out different apps can be a frustrating experience where expectations may not be met. It is easy to be contented by the rewards and small achievements of vocabulary development or grammar drills without stopping to think about whether those steps are leading in the right direction to achieve specific language learning goals. This entry presents the many ways that learners can use apps to support their language learning and outlines a methodology to develop app literacy to make informed decisions on how they can best use their time to support specific needs for their personal language learning goals, to maintain motivation and to challenge themselves.