The short version
Medito and Insight Timer are the two best free meditation apps. Medito is free with no strings at all. Insight Timer is free with a huge library and an optional paid tier. Pick Medito for simplicity and privacy; pick Insight Timer for range.
What each one is
Medito is built by the Medito Foundation, a registered charity. Every session is free — guided meditations and courses, sleep stories and sounds, breathing exercises, stress and anxiety sessions and an unguided timer. There are no ads, no account and no premium tier, and the code is public.
Insight Timer works like a large open platform for meditation teachers. It lists 360,000 free tracks from psychologists, mindfulness teachers and spiritual leaders, plus live events and a community. Member Plus (US$60 per year, 7-day free trial) adds thousands of 10- and 30-day courses, offline listening and higher-quality audio.
Who should pick which
Choose Medito if you want to open an app and meditate, with nothing to sign up for, nothing to upgrade and a library small enough not to overwhelm. Choose Insight Timer if you like exploring different teachers, traditions and session lengths, and you are willing to do some curating — quality varies more on an open platform.
What the evidence says
Studies of app-based mindfulness show modest benefits for stress and wellbeing on average, but results are mixed and depend heavily on regular use. Neither app has been shown to outperform the other, and meditation is not a treatment for any condition; a small number of people find it unsettling — see meditation safety and adverse effects. Consistency matters more than which library you use; how much meditation you need covers the practical side.
Bottom line
Both apps make paying optional. Medito is the cleanest, most private free choice; Insight Timer gives you far more choice for free and a cheap upgrade if you want courses. For the wider field, see our meditation app ranking or Calm vs Insight Timer.