DeepSeek: a plain-English guide

What DeepSeek is and who makes it

DeepSeek is a Chinese AI company based in Hangzhou, backed by the quantitative investment firm High-Flyer. It makes large language models and a free chat assistant of the same name. DeepSeek became world-famous in early 2025, when its R1 reasoning model matched much more expensive Western models on many tasks while its weights were published for anyone to download. That combination of strong results, low cost and openness is still what DeepSeek is known for.

Unlike most leading American labs, DeepSeek releases the weights of its main models under the permissive MIT license. That means developers and companies can download them, run them on their own servers, fine-tune them and use them commercially.

The DeepSeek model family

DeepSeek's lineup is simpler than most, but it changes quickly. The main lines are:

• The V series. General-purpose models used for chat, writing, coding and reasoning. As of October 2026, the current generation is V4.1, and the first model in it, V4.1-Flash, is a large mixture-of-experts model with native image understanding and a very long context window.
• Flash and Pro sizes. DeepSeek offers a faster Flash size and a larger Pro size. It has said a V4.1 Pro model is coming; until then, its API sends Pro requests to V4.1-Flash.
• R1 and reasoning. R1 helped popularize open reasoning models that "think" before they answer. Today that ability is built into the main models as a thinking mode you can switch on.

"Mixture-of-experts" means that only part of the model is active for each word it produces, which makes very large models cheaper to run. Even so, the full DeepSeek models are far too large for a normal laptop; self-hosting them takes data-center hardware.

What DeepSeek is good at

• Math, logic and coding. DeepSeek's models are particularly strong at step-by-step problem solving, programming and debugging.
• Low-cost API access. DeepSeek's developer API is known for low prices, which makes it popular for apps that send a lot of requests.
• Open weights. Because the weights are public under MIT, companies can run DeepSeek privately, adapt it to their field, or build products on it without paying DeepSeek.
• A free chat app. The official web chat and mobile apps are free and include web search, file uploads and a thinking mode for harder questions.
• Chinese and English. It works well in both and handles many other languages.
• Long inputs. The current models can take very long documents or large chunks of code in one request.

Limits to keep in mind

DeepSeek can be wrong, like any AI model, and its thinking mode can sound convincing even when the reasoning has a gap. Check facts and test code before you rely on it; see our guide on fact-checking AI answers.

The official DeepSeek app and website follow Chinese content rules, so they avoid or deflect some politically sensitive topics. Self-hosted copies of the open weights are not filtered the same way, but they still reflect their training. The consumer app also has fewer extras than the biggest Western assistants: image and video creation and a large ecosystem of add-ons are not its focus. At busy times, the free service can be slow.

How to use DeepSeek officially

The official ways to use DeepSeek are the web chat on DeepSeek's website, the DeepSeek apps for iPhone and Android, and the DeepSeek API for developers, which follows the same request format as OpenAI's API. DeepSeek also offers a desktop agent app called DeepSeek Harness for longer tasks on your computer. The open weights are published on Hugging Face, and many cloud providers host DeepSeek models too. Download apps only from official stores or links, because copycat apps using the DeepSeek name are common. The official link in the facts section of this page goes to DeepSeek's site.

Privacy notes

This is the most important difference between DeepSeek's own service and its open weights. DeepSeek's privacy policy says it collects, processes and stores personal data in the People's Republic of China, so data you type into the official app or API is handled under Chinese law. The policy says DeepSeek may use your data to train and improve its models, and it lists a right to opt out of that use. Some governments and organizations have restricted the official app on work devices for these reasons.

If you run the open weights yourself, or use a host you trust in your own region, your prompts never go to DeepSeek at all. Either way, avoid entering passwords, ID numbers, health data or confidential business information into any public chatbot. Our AI privacy and safety guide explains why.

How DeepSeek compares

Compared with ChatGPT, DeepSeek offers open weights and very low API prices, while ChatGPT has more features, polished apps and data handled under US law. Among open-weight families, Qwen offers more model sizes, including ones small enough for a laptop; Llama has a long track record and huge tool support; and Mistral is a European alternative. For a detailed look, read ChatGPT vs DeepSeek.

FAQ

Is DeepSeek free?

The official chat website and apps are free to use. The developer API is paid per use, and the open weights are free to download, although running them needs powerful hardware.

Is DeepSeek open source?

Its main models are open-weight: the trained weights are published under the MIT license, which allows commercial use. The full training data is not published, so some people prefer the term "open-weight" over "open source".

Is it safe to use DeepSeek?

It depends on what you share and how you use it. The official service stores data in China, so keep sensitive information out of it. Self-hosting the weights keeps your data under your control.

Can I run DeepSeek on my own computer?

Not the full models, which need data-center hardware. Smaller community versions and distilled models exist, but they are less capable than the full models.

Is ChatG related to DeepSeek?

No. ChatG is an independent AI chat website and is not affiliated with DeepSeek. This page is an informational guide. You can try ChatG free in your browser.