Sotto

Overview

Sotto is an open-source language-learning app built around CEFR courses and practice on infrastructure you control. It will suit learners who want to connect study with their own reading and interests, and who are prepared to run the software themselves. Its structured curriculum and adaptable provider options are compelling; self-hosting and provider costs make it less suited to anyone seeking a ready-to-use service.

Key features

Courses cover grammar, reading, listening, speaking, and writing, with advancement gated by demonstrated mastery. That gives learners a defined path through core skills, while ungated practice lets them work on a particular area without waiting to pass a course milestone. A placement test helps establish a starting point.

Sotto tracks vocabulary and grammar in a per-course memory graph and uses SM-2 spaced repetition to schedule reviews and inform adaptive listening. The link between review and listening gives practice continuity, though the system’s value depends on having a course and practice routine to feed it.

Learners can create classes from articles, papers, YouTube links, or topics, with material leveled to their CEFR course and citations provided. This makes Sotto especially relevant to people who want language study grounded in their work or interests. Its mock exams follow Goethe, DELE, Cambridge English, or general CEFR formats, but provide practice feedback rather than official scores.

AI and speech services are configurable: options include OpenAI and Anthropic API keys, local Claude Code or Codex agents, and local Ollama, faster-whisper, and Kokoro components. Gemini Live supports real-time spoken translation, and an MCP server connects Claude Code or Codex workflows. The breadth is useful for technically confident learners who want control over providers; it also means choosing, configuring, and potentially paying providers is part of the experience.

The application, database, and files run on the operator’s stack. A fully offline setup can keep language-model, speech-recognition, and speech-generation components on the learner’s own hardware. Content sent to configured cloud providers is governed by their terms. Per-account API keys are encrypted at rest using BYOK_ENCRYPTION_KEY. Self-hosted access uses a shared password and local learner profiles, with optional WebAuthn passkeys that an administrator can revoke.

Pricing

There is no software charge for the self-hosted plan, but it is not necessarily cost-free if you use paid provider services. The license also requires redistributed versions to remain under the same terms. A managed hosted offering is planned, so the current choice is for users willing to operate their own setup.

Platforms

Sotto offers an installable browser PWA and a desktop launcher for macOS, Windows, and Linux; Windows setup uses WSL2. Mobile apps are supported, with the web app available on phones and tablets. The maker also provides an iPad workbook PDF for annotation in GoodNotes or another app, and a Rust terminal client with audio playback and microphone recording. The native iPad app targets iPadOS 18 or later.

Who it's for

Sotto is a strong fit for independent learners who want structured CEFR progression, speaking rehearsal, and lessons drawn from personal material without handing their entire application and database to a hosted platform. Its private practice also suits people who want to prepare before speaking with a teacher, tutor, classmate, or stranger. It is a weaker choice for learners who want minimal setup, do not want to manage provider accounts, or need official exam scores.

Pros and cons

• Pro: Mastery-gated courses span five skills, while ungated practice makes it possible to target a skill directly.
• Pro: Spaced repetition informs adaptive listening, and source-based classes connect study to material the learner chooses.
• Pro: Self-hosting and offline components give technically capable users substantial control over where the application and practice run.
• Con: Users must run the infrastructure themselves and may owe configured AI and speech providers directly.
• Con: Windows setup requires WSL2, adding a setup step for Windows learners.
• Con: Mock-exam feedback is for practice, not an official score.

Alternatives

Duolingo is worth choosing instead for a freemium app with Android, iOS, macOS, and web access, plus a free plan and a one-week free trial.

Busuu is another freemium option, with a free plan and Android, iOS, and web platforms; it may suit learners looking for a different app-based route.

Learning with Texts is a free, self-hosted alternative for Linux, macOS, Windows, and web users who can run a local web server with PHP and MySQL.

LingQ may be a better fit for learners who want Android, iOS, web, or browser-extension access and can work within its free membership limits of 20 saved words and phrases, five imported lessons, and one audio playlist.

mLearn offers a free option across mobile, desktop, and browser-extension platforms; its optional cloud features have usage limits, and voice mode with character cloning requires cloud quota.

TextLingo 2 is a freemium alternative across Android, iOS, Linux, macOS, web, and Windows, with a free tier capped by credits, article and novel counts, memorization quota, article segments, and novel size.

LearnEnglish Grammar is a narrower alternative for Android and iOS users looking for free grammar practice; its app includes ads and in-app purchases.

Talkpal may suit learners who want AI conversation practice on Android, iOS, or web, though its free Basic Plan has a 10-minute daily limit.

For more options, browse language learning apps.

Verdict

Choose Sotto if you want a mastery-based CEFR course, adaptive review, and speaking practice built around your own material—and are willing to operate a self-hosted setup. Its strongest advantage is the combination of learner-controlled infrastructure and configurable AI and speech. Look elsewhere if you need a hosted service that is ready without setup, or prefer not to manage provider accounts and possible service charges.