What Is DeepSeek AI? How to Use It (Complete Guide 2026)

In early 2025, a Chinese AI company called DeepSeek launched a model that sent shockwaves through Silicon Valley. Here was an AI that could match — and in some cases outperform — GPT-4o and Claude 3.5, developed at a reported cost of just $5.6 million, compared to the hundreds of millions OpenAI spent training GPT-4.

The tech world called it a "Sputnik moment" for American AI dominance. NVIDIA's stock dropped 17% in a single trading session. And millions of users immediately asked: what exactly is DeepSeek, and how can I use it?

What Exactly Is DeepSeek?

DeepSeek (深度求索, meaning "seeking deep understanding") is a Chinese AI research company founded in 2023, funded by quantitative hedge fund High-Flyer Capital Management. Their mission was to build frontier AI models focused on research and reasoning efficiency.

They've released several notable models:

• DeepSeek-V2 — A mixture-of-experts model that demonstrated exceptional efficiency
• DeepSeek-V3 — Their flagship general-purpose model, competitive with GPT-4o on most benchmarks
• DeepSeek-R1 — A reasoning model that uses chain-of-thought to work through complex problems, competitive with OpenAI's o1
• DeepSeek-R1-Zero — A version trained purely through reinforcement learning, without supervised fine-tuning

DeepSeek R1: The Reasoning Model That Changed Everything

DeepSeek R1 is arguably the most significant AI release since GPT-4. Here's what makes it special:

Chain-of-Thought Reasoning

Unlike standard language models that generate answers directly, R1 reasons through problems step by step before producing a final answer. You can watch it think — it shows its reasoning process, then delivers a conclusion. This approach dramatically improves performance on:

• Complex mathematics (IMO-level problems)
• Software engineering tasks
• Multi-step logical reasoning
• Scientific analysis

Open Source

DeepSeek R1 is released under the MIT licence — one of the most permissive open-source licences available. This means anyone can:

• Download and run it locally on their own hardware
• Fine-tune it for specific applications
• Use it commercially in products without paying licensing fees
• Inspect the model weights (partially) to understand its behaviour

How to Use DeepSeek (3 Ways)

Method 1: DeepSeek Chat (Free Web App)

The simplest way — no technical knowledge required:

1. Go to chat.deepseek.com
2. Create a free account with your email
3. Start a new conversation
4. For reasoning tasks, select "DeepThink (R1)" mode to see the step-by-step reasoning

Method 2: DeepSeek Mobile App

1. Download DeepSeek from the App Store or Play Store
2. Sign in with your account
3. The app includes voice input, image upload, and file analysis

Method 3: API for Developers

DeepSeek offers an OpenAI-compatible API, which means if you're already using the OpenAI Python SDK, you can switch to DeepSeek by just changing the base URL and API key:

from openai import OpenAI

client = OpenAI(
    api_key="your-deepseek-api-key",
    base_url="https://api.deepseek.com"
)

response = client.chat.completions.create(
    model="deepseek-chat",
    messages=[{"role": "user", "content": "Explain quantum entanglement simply"}]
)
print(response.choices[0].message.content)

The API is priced at a fraction of OpenAI's rates — approximately $0.14 per million input tokens for DeepSeek-V3, compared to $5.00 for GPT-4o.

Running DeepSeek Locally (Completely Offline)

Because DeepSeek models are open-source, you can run them entirely on your own machine. The easiest method:

Using Ollama (Recommended)

1. Install Ollama from ollama.ai
2. Open your terminal and run: ollama run deepseek-r1:7b (7B version for most PCs)
3. For more powerful machines: ollama run deepseek-r1:32b
4. Ollama downloads the model and starts a local server automatically

Running locally means: zero data privacy concerns, no API costs, and the ability to use it offline.

DeepSeek vs. ChatGPT vs. Claude: Full Comparison

Privacy Concerns with DeepSeek

DeepSeek's rise has also attracted scrutiny. Being a Chinese company, some users and governments have raised data privacy concerns:

• Italy's data protection authority temporarily restricted DeepSeek over data storage concerns
• Some US government agencies and defence contractors have restricted its use
• DeepSeek's privacy policy indicates data may be stored on servers in China

Practical guidance: For general use, coding help, and non-sensitive tasks, DeepSeek is perfectly safe. For sensitive enterprise or government data, run it locally via Ollama (no data leaves your machine) or use a Western provider.

Best Use Cases for DeepSeek in 2026

For Developers

• Code review and debugging — Paste complex bugs and see R1 reason through them step by step
• Architecture planning — Ask DeepSeek to evaluate system design trade-offs
• Regex patterns and JSON debugging — Combined with tools like Regex Tester and JSON Formatter for a powerful workflow

For Students and Researchers

• Complex math and proofs — DeepSeek R1 explains its reasoning, making it excellent for learning
• Research paper analysis — Upload PDFs and get structured summaries

For Businesses

• Cost-effective API integration — Build AI-powered features at a fraction of OpenAI's cost
• Private deployment — Run on your own servers for full data control

Frequently Asked Questions

Conclusion

DeepSeek has fundamentally changed the AI landscape by proving that frontier-level AI doesn't require billions of dollars in compute spending. Its combination of open-source availability, exceptional reasoning capabilities, and near-zero API cost makes it an extraordinary resource for developers, students, and businesses.

Whether you use it on the web at chat.deepseek.com, via the API, or run it locally for complete privacy — DeepSeek is worth exploring. Combine it with developer tools like JSON Formatter for a powerful AI-assisted workflow.