Yi (01.AI)

Freemium

01.AI's open-weight LLM family founded by Kai-Fu Lee with strong bilingual Chinese/English performance

What is Yi (01.AI)?

01.AI is the AI startup founded by Kai-Fu Lee in 2023 that quickly became one of China's most notable LLM labs, releasing the Yi model family as open-weight models with strong bilingual Chinese and English capabilities. Yi models have shipped in multiple generations: Yi-6B, Yi-9B, Yi-34B (which briefly led the Hugging Face Open LLM Leaderboard), Yi-VL vision variants, and the Yi-Large flagship that powers 01.AI's commercial API. The Yi family is built on a Llama-compatible architecture, which means it plugs into the entire Llama tooling ecosystem — vLLM, Ollama, LM Studio, Hugging Face Transformers, and llama.cpp all support Yi out of the box with no special handling. Yi's open checkpoints use a permissive license that allows commercial use with some acceptable-use provisions. Where Yi really shines is bilingual performance: it is one of the strongest openly-available models for Chinese language tasks while maintaining competitive English capabilities, making it a go-to choice for applications targeting Chinese-speaking users, translation, and multilingual RAG systems. 01.AI also operates a hosted API for Yi-Large and Yi-Lightning with competitive pricing. For developers who want frontier-class open Chinese-English models that just work with existing Llama tooling, Yi is arguably the strongest pick alongside Qwen and DeepSeek.

⚡ Quick Verdict

Best for

Bilingual Chinese/English applications and teams needing strong open models with Llama-compatible architecture

Not ideal for

English-only users who want the biggest fine-tune ecosystem

Starting price

Free weights · Hosted API from ~$0.21/M tokens

Free plan

Yes — open weights are free

Key strength

Best-in-class bilingual Chinese/English performance in an open-weight LLM

Limitation

Smaller English community than Llama or Mistral

Bottom line: Yi scores 4.3/5 — the top open-weight choice for bilingual Chinese/English applications. Choose Yi-34B for general use, Yi-34B-200K for long documents.

Pricing

Open weights — Free: Yi-6B, Yi-9B, Yi-34B, and Yi-VL variants can be downloaded from Hugging Face or 01-ai on GitHub under the Yi Series Models Community License. Commercial use is permitted with standard acceptable-use conditions.

01.AI hosted API: Yi Base 6B around $0.21 per million tokens on AI/ML API marketplaces. Yi-Large and Yi-Lightning are available via platform.01.ai with usage-based pricing.

Third-party inference: Together AI, Fireworks, and OpenRouter host Yi-34B and smaller variants at competitive per-token rates. Self-hosting is free beyond hardware costs.

Key Features

Yi-6B, Yi-9B, Yi-34B open checkpoints
Yi-VL vision variants with multimodal understanding
Yi-Large commercial API flagship model
Llama-compatible architecture — works with all Llama tooling
Class-leading bilingual Chinese/English performance
200K context window support in Yi-34B-200K variant
Backed by Kai-Fu Lee and Sinovation Ventures
Apache-style permissive open license

Pros & Cons

Pros

Best-in-class open model for Chinese language tasks
Llama-compatible — instant ecosystem support
200K context window in the 34B-200K variant
Active model updates and strong English performance too

Cons

Smaller English-language ecosystem than Llama
Fewer fine-tunes and community derivatives
Less frequent releases than Qwen in recent months

✅ Pricing verified April 2026 · ✅ Independently reviewed · ✅ Scoring methodology

FAQ

Who is behind 01.AI?

01.AI was founded in 2023 by Kai-Fu Lee, a well-known AI researcher who previously led Google China and Microsoft Research Asia. The company is backed by Sinovation Ventures and reached unicorn status within nine months of founding, with a mission to build globally competitive open-weight LLMs from China. The Yi model family is 01.AI's flagship output.

Is Yi better for Chinese than Qwen?

Both Yi and Qwen are excellent for Chinese language tasks, and the winner depends on the specific benchmark. Qwen currently has more frequent updates and a larger ecosystem, while Yi is sometimes preferred for bilingual Chinese-English tasks where maintaining English quality matters. For most production Chinese deployments, try both on your specific workload and pick the one that scores higher.

Does Yi work with Ollama and LM Studio?

Yes, smoothly. Yi uses a Llama-compatible architecture, so any tool that loads Llama models — Ollama, LM Studio, llama.cpp, vLLM, Hugging Face Transformers — supports Yi out of the box. Just use the 01-ai/Yi-34B or similar model ID.

What is Yi-34B-200K?

Yi-34B-200K is a long-context variant of Yi-34B that supports up to 200,000 tokens of input context. It is designed for document analysis, long-form RAG, and any workload that benefits from very long prompts. At release it was one of the first openly available 200K-context models, and it remains competitive for open-weight long-context use cases in 2026.

How does Yi-Large compare to GPT-4?

Yi-Large is 01.AI's frontier commercial model offered via their hosted API. It scores competitively with GPT-4 on several Chinese benchmarks and performs respectably on English benchmarks, though it still trails the very latest frontier models from OpenAI, Anthropic, and Google. For Chinese-first applications, Yi-Large is one of the strongest options.

Can I fine-tune Yi commercially?

Yes. The Yi Series Models Community License permits commercial fine-tuning, redistribution of fine-tuned weights, and deployment in commercial applications. Acceptable-use conditions apply but the license is broadly compatible with normal business use.