DeepSeek

DeepSeek is a free AI chatbot that shot to global attention in early 2025 by matching leading models on coding, maths and reasoning while training far more cheaply. Its web and mobile chat offers a general assistant plus DeepThink, a step-by-step reasoning mode for hard problems, alongside web search and file upload for summarising documents.

Key facts: DeepSeek's models are open-weight under an MIT-style licence, so developers can self-host distilled versions or build on them, and its API is OpenAI-compatible for easy switching. The model line has moved fast: V3 launched in late 2024, the R1 reasoning model followed in January 2025, and the V4 family arrived in 2026. The chatbot itself is free to use on the web and in the app.

Plans: Chat on the web and mobile apps is free, with no subscription for the standard assistant. The developer API is separate and pay-as-you-go, priced per million tokens — far below most frontier rivals — so check the official platform page for current rates before building on it.

Best for: anyone who wants a genuinely free, strong general chatbot, especially for coding help, maths and step-by-step reasoning, and developers who value open weights. Watch out: the free service can show "server busy" errors at peak times, and its servers are in China, so avoid pasting sensitive work data into it. Who should skip it: anyone who needs to paste sensitive work data into a chatbot, given its servers are in China.

Pros

• A genuinely free chatbot on web and mobile, with no subscription for the standard assistant
• Strong on coding, maths and step-by-step reasoning through its DeepThink mode
• Web search and file upload for summarising documents
• Open-weight models under an MIT-style licence, with an OpenAI-compatible API for easy switching

Watch out for

• The free service can show 'server busy' errors at peak times
• Its servers are in China, so avoid pasting sensitive work data into it
• The developer API is separate and pay-as-you-go, so API use is not free

Pricing

Chat on the web and mobile apps is free, with no subscription for the standard assistant. The developer API is separate and pay-as-you-go, priced per million tokens, far below most frontier rivals, so check the official platform page for current rates before building on it.

FAQs

Is DeepSeek really free? Yes, chat on the web and mobile apps is free; only the developer API is pay-as-you-go.

What is DeepThink? A step-by-step reasoning mode for hard problems.

Can developers self-host DeepSeek models? Yes, its models are open-weight under an MIT-style licence, so developers can self-host distilled versions.