What Is DeepSeek AI? A Plain Guide for 2026

What Is DeepSeek AI? A Plain Guide for 2026

DeepSeek is a Chinese AI company from Hangzhou that builds large language models on par with ChatGPT, Claude and Gemini — but releases them openly under the MIT license and charges far less for them. The chat service is free, the models can be downloaded and run on your own hardware, and when the company's R1 model arrived in January 2025 it wiped almost 600 billion dollars off Nvidia's market value in a single day.

Below we cover who is behind DeepSeek, which models exist in 2026, what it costs, whether it is safe to use with business data, and how it compares with ChatGPT. If terms like parameters and open weights are new, we explain them in what an LLM is.

What is DeepSeek?

DeepSeek is both a company and the name of its AI models and chat app. When people say they "use DeepSeek" they usually mean the chat service at chat.deepseek.com or the mobile app — a direct counterpart to ChatGPT where you ask questions and get answers.

A few facts about the company:

• Founded: July 2023, in Hangzhou in eastern China.
• Founder: Liang Wenfeng, who also runs the hedge fund High-Flyer. The fund owns and finances DeepSeek — not venture capital or a tech giant.
• Size: around 160 employees in 2025, a small team next to OpenAI, Google or Anthropic.
• Model: the weights are released openly under the MIT license. Anyone may download, modify and use them commercially.

That last point is what sets DeepSeek apart from its American rivals most. ChatGPT and Claude can only be used through their makers' own services. DeepSeek can run on your own server, in a European cloud or on a powerful workstation, without any text passing through China.

Why did DeepSeek shake the stock markets in January 2025?

On 20 January 2025 DeepSeek released R1, a model that reasons its way through several steps before answering — the same kind as OpenAI's o1. It matched o1 on maths and programming. Two things made it land like a bomb:

1. The price. The underlying V3 model was reportedly trained for under 6 million dollars, a fraction of what American labs spend. R1 was also 20 to 50 times cheaper to use than o1.
2. The openness. The whole model was released freely. The American lead, which rested on nobody else being able to afford it, suddenly looked much smaller.

The DeepSeek AI Assistant app became the most downloaded free app in Apple's US App Store that same week, ahead of ChatGPT. The same happened in Sweden. On 27 January Nvidia's stock fell 17 percent — the largest single-day loss of market value for any company in US history. The market suddenly priced in the idea that AI might not need as many expensive chips as everyone had assumed.

The scepticism came just as quickly. Critics argued that the 6 million figure covered only the final training run, not research, staff or hardware. There were also questions about how the company obtained Nvidia chips covered by US export controls. OpenAI has accused DeepSeek of training on output from OpenAI's models, but has not presented evidence publicly.

Which DeepSeek models exist in 2026?

DeepSeek has shipped models at a rapid pace since the breakthrough. The timeline:

• DeepSeek-V3 (December 2024) — the general model everything built on.
• DeepSeek-R1 (January 2025) — the reasoning model that started the uproar. Updated in May 2025.
• DeepSeek-V3.1 (August 2025) — merged V3 and R1 into one model that can switch between answering directly and thinking first. There has been no separate R model since.
• DeepSeek-V3.2 (December 2025) — more efficient handling of long texts.
• DeepSeek-V4 (preview April 2026) — two sizes, V4-Pro and V4-Flash, with a one-million-token context window. Flash went official in July and Pro in August 2026, with clearly better coding and agent abilities.
• DeepSeek-V4.1-Flash (September 2026) — the latest, which also understands images.

The much-discussed R2 never arrived as a model of its own. Reasoning was built into the main models instead.

Much of the secret behind the low cost is a technique called Mixture of Experts: the model is made of many specialised parts, and only a small share is used for each word. V3 has around 671 billion parameters but uses roughly 37 billion at a time. We explain how that works in Mixture of Experts — how the technique makes AI cheaper.

Is DeepSeek free? What does it cost?

The chat service and the app are free. You create an account and can use the latest model without a subscription. There is no paid tier like ChatGPT Plus.

The models are free too, in the sense that you may download them and run them yourself, even commercially. What you pay for then is hardware. The large models need several server GPUs; smaller, distilled versions exist for an ordinary computer.

The API costs money, but not much. This was the price per million tokens (about 750,000 words) in September 2026:

• DeepSeek Flash: $0.30 input, $1.20 output
• DeepSeek V4-Pro: $1.32 input, $3.96 output

Prices are halved outside DeepSeek's peak hours, and input that has already been sent once (cache) costs almost nothing. For comparison, the leading American models often charge 5 to 20 times more for the same amount of text. Always check current prices on DeepSeek's own site before budgeting a project.

Is DeepSeek safe? Data, GDPR and censorship

This is the most important question for a European business, and the answer depends entirely on how you use DeepSeek.

The app and the chat at deepseek.com send your text to servers in China. Under DeepSeek's own terms the data is stored there, and Chinese law can compel companies to hand information to the authorities. Several European data protection authorities have reacted:

• Italy blocked DeepSeek from processing Italians' personal data in January 2025.
• Berlin's data protection commissioner declared in June 2025 that transferring user data to China violates the GDPR, and asked Apple and Google to remove the app in Germany.
• Authorities in France, Ireland, Belgium and the Netherlands, among others, have opened investigations.

The downloaded model is something else entirely. Run DeepSeek on your own server or with a European cloud provider and the data never leaves the EU. The model itself sends nothing anywhere. That distinction is often missed in the debate: the problem is the service, not the technology.

One thing comes along however you run it: censorship. DeepSeek is trained to avoid or slant questions about Chinese politics — Tiananmen, Taiwan, Xinjiang. For most work tasks it does not matter, but it is worth knowing if the model is meant to answer questions about the world.

Our advice: never paste customer data, personal data or trade secrets into DeepSeek's app. If you want to use the models in your business, run them in your own environment. We go through how that works in practice in the best open source LLMs of 2026.

How good is DeepSeek in other languages?

DeepSeek is strongest in English and Chinese, which dominate its training data. It understands and writes smaller languages such as Swedish well enough for everyday tasks — summarising a text, explaining a concept, writing a draft.

The gap to the largest American models is more visible there, though. The text is more often stiff or literally translated, and English or Chinese words occasionally slip in. When we had five chatbots write the same text in our AI chatbot comparison, DeepSeek was also clearly the slowest. The models have improved a lot since then, but for text you will publish in a smaller language, ChatGPT or Claude is still the safer choice.

DeepSeek vs ChatGPT — what is the difference?

• Company: DeepSeek is Chinese; ChatGPT comes from America's OpenAI.
• Chat price: DeepSeek is free. ChatGPT is free with limits, and Plus costs $20 a month.
• Open model: DeepSeek yes, under the MIT license. ChatGPT no.
• Self-hosting: DeepSeek can run in your own environment. ChatGPT cannot.
• Where app data ends up: DeepSeek in China. ChatGPT in the US, with EU residency for business customers.
• API price: DeepSeek is very cheap, ChatGPT considerably more expensive.
• Smaller languages: good in DeepSeek, very good in ChatGPT.
• Images, voice and tools: limited in DeepSeek, a broad range in ChatGPT.

In short: ChatGPT is the better finished product, with more features and stronger language quality. DeepSeek is the better building block for anyone who wants a powerful model cheaply, or to run it themselves so the data stays in-house.

How do you get started with DeepSeek?

There are four routes, from simplest to most control:

1. The chat at chat.deepseek.com — log in and start typing. Good for trying it, not for sensitive information.
2. The app for iPhone and Android — the same thing on your phone.
3. The API via platform.deepseek.com — for developers who want to build the model into their own services. It is compatible with both OpenAI's and Anthropic's interfaces, so existing code can often simply be pointed at it.
4. Self-hosting — download the weights from Hugging Face and run them with, for example, Ollama or vLLM, or pick a European provider that already runs them for you. It is the only option where you have full control over the data.

What does DeepSeek mean for businesses?

DeepSeek's biggest mark may not be the app but what it did to the market. Since January 2025 the price of AI has fallen sharply, and open models from China now sit close to the closed American ones. You no longer have to choose between an expensive top model and a poor cheap one.

At the same time the choice gets harder: which model, in which environment, with which data? That is the question we help with as an AI consultant — from deciding whether an open model is enough for your needs to building the solution that runs it.