Everything you need to know about Flex
Flex is an iOS app designed to help you master Spanish verb conjugations through scientifically-proven spaced repetition. Using the FSRS (Free Spaced Repetition Scheduler) algorithm, Flex optimizes your learning by showing you conjugations at the exact moment you're about to forget them, maximizing retention while minimizing study time.
Flex is short for inflexión / inflexion:
Usage note: British spelling; American English typically uses inflection.
Since Flex focuses on mastering Spanish verb conjugations, the systematic inflection of verbs for person, number, tense, mood, and aspect, the name captures exactly what the app teaches.
Spaced repetition is a learning technique that presents information at increasing intervals. When you correctly recall a conjugation, Flex schedules the next review further in the future. If you struggle, it appears sooner. This adaptive approach ensures efficient memorization by leveraging the psychological spacing effect.
Flex uses the FSRS algorithm, which has been shown to outperform traditional spaced repetition systems by adjusting to your individual learning patterns.
Flex includes comprehensive coverage of Spanish verb conjugations across all major tenses and moods:
The app covers 5,064 Spanish verbs, more than twice what competitors offer, including irregular verbs and stem-changing patterns.
Yes! Flex supports 21 regional varieties of Spanish, including comprehensive voseo coverage that other apps ignore entirely or oversimplify. Flex includes 6 distinct vos varieties plus sumercé:
Each variety is fully conjugated with proper pronouns (tú/vos/vosotros) and regional phonology. Competitors like Ella Verbs ignore vos entirely, while ConjuGato supports only 1.5 varieties (Argentina and simplified Chile).
Absolutely. Flex includes a speaking mode with on-device speech recognition that works completely offline. Two engines are available:
Both engines use smart matching that handles common recognition quirks like b/v swaps, dropped trailing letters, and vowel confusion. Unlike competitors like Ella Verbs (which use server-based recognition with rate limits and an inferior offline fallback) or ConjuGato (no speaking mode at all), everything runs entirely on your device. No internet required.
Flex is designed for learners at all levels. Whether you're just starting to learn Spanish conjugations or refining advanced tenses, you can customize which verbs and tenses to study. The spaced repetition system adapts to your current knowledge, making it effective for both beginners and advanced students.
Flex is free to use with all 5,000+ Spanish verbs in Present Indicative tense. The Pro upgrade unlocks all 23 tenses and moods (including subjunctive, imperative, compound tenses, and more) with a one-time purchase. No subscriptions. Pay once, own forever.
Currently, Flex is available exclusively for iOS (iPhone and iPad). We're evaluating demand for an Android version. If you'd like to see Flex on Android, please let us know at support@flexlanguage.app.
For questions, feedback, or technical support, email us at support@flexlanguage.app. We typically respond within 24-48 hours.
Yes! Everything in Flex works completely offline, including speech recognition, which runs entirely on-device using OpenAI Whisper and Apple Speech. All 5,064 verbs, conjugations, study data, and even text-to-speech voices (from Argentina, Chile, Colombia, Mexico, and Spain) are stored locally.
This is a major advantage over competitors like Ella Verbs, which requires internet for speech features with server-based rate limits (and only offers an inferior offline fallback).
Flex is dramatically overbuilt, just plain better, both technically and linguistically. Here's how we compare:
We gave Flex an A+, Ella a C, and ConjuGato an F. See the full comparison table for details.
The deck counts show different card states using color coding:
The FSRS algorithm schedules reviews at optimal intervals based on your performance. Cards you find easy will appear less frequently, while difficult cards appear more often until you've mastered them.
The glossary contains detailed English and Spanish entries for over 5,000 verbs. Each word includes:
Yes. Tap the question mark icon in the upper left of the deck selection screen to open a comprehensive help guide. It covers deck counts, tenses and moods (with definitions and Spanish examples for every tense), study flow and rating buttons, FSRS spaced repetition, filters, presets, speech recognition, the glossary, regional dialects, and Pro features.
Flex includes detailed statistics showing your learning progress, including cards studied, accuracy rates, retention metrics, and study streaks. You can see which tenses you've mastered and where you need more practice.