Anki

Anki is the tool serious memorizers settle on, and for good reason: its spaced-repetition algorithm — showing each card right as you're about to forget it — remains the most effective approach to long-term retention available, and it's why medical students grinding USMLE decks and language learners banking thousands of words keep coming back to it. It's also remarkably capable under the hood, handling 100K+ card decks without lag and supporting audio, images, LaTeX, image occlusion, and cloze deletion, plus a deep add-on ecosystem and thousands of shared community decks. The honest friction is real, though: the interface looks like it's from another era, and the learning curve — note types, deck options, scheduling settings — is genuinely steep before it clicks. And while it's free on desktop and Android, the iOS app is a one-time $24.99, which catches people off guard. This is not a polished, frictionless app; it's a powerful, slightly utilitarian one that rewards the effort you put into learning it. For anyone whose goal is to remember a large body of material for years rather than days, it's worth every bit of that effort — and still free where it counts.