Anki

Anki is the top-rated language learning app among self-reported fluent speakers, outperforming #2 italki in retention efficiency. Its spaced repetition algorithm, grounded in over 90 years of memory research, boosts long-term recall by up to 50% compared to traditional methods. With over 10,000 shared decks across 100+ languages, Anki enables learners to memorize 200-300 new words monthly. Despite its dated interface—resembling software from 2003—it remains the gold standard for vocabulary retention. Free on desktop and Android, with a $25 one-time iOS fee, it offers a cost-per-word efficiency of less than $0.01, making it 5x cheaper than the average subscription app.