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DeepSeek

DeepSeek guide for practical AI users

A low-cost AI assistant and open-weight model family from a Chinese AI lab, used for chat, coding help, and research at a fraction of the price of larger providers.

Quick take

DeepSeek offers a free chat app, downloadable model weights, and two current API versions: V4 Flash 0731 and V4 Pro 0813. Its token rates are low but vary by time of day. The real trade-off is data governance: the hosted service is subject to Chinese law, so sensitive business data needs care.

Best fit

Use DeepSeek when cost is a real constraint and you still want good reasoning or coding output. It fits developers testing ideas cheaply, cost-conscious founders, and technical teams that can self-host the open weights when data control matters.

First setup

1

Open the DeepSeek web app or install the mobile app and sign in to use the chat for free.

2

For building, create an account on the DeepSeek API platform, generate an API key, and check the current balance and billing rules before sending traffic.

3

Pick a model on purpose: the lighter model for fast, cheap tasks and the heavier model when a job needs deeper reasoning.

4

Keep repeated system prompts and document prefixes exactly the same so DeepSeek's automatic context cache can recognize them.

5

If you need full data control, download the open weights from the official model pages and run them on your own hardware or a private host.

Workflows worth trying

Cut API costs on a repetitive task

Useful when you run the same kind of prompt many times a day, such as tagging tickets, drafting replies, or pulling fields out of text.

  1. Write one clear prompt with a fixed instruction block and a slot for the changing input.
  2. Send it through the lighter model first and check the output quality on real examples.
  3. Keep the fixed instruction block byte-for-byte stable so the automatic cache can recognize it.
  4. Move the task to the heavier model only if the lighter one misses on cases that matter.

Get a second opinion on code

Useful for founders and developers who want a cheap review before shipping a change.

  1. Paste the function or file and say what it should do and what you are unsure about.
  2. Ask DeepSeek to find bugs, edge cases, and unclear names, and to explain its reasoning.
  3. Ask for a corrected version with comments on what changed and why.
  4. Test the change yourself before you commit it.

Prompt recipes

Cheap structured extraction

From the text below, return only JSON with these fields: [field list]. If a field is missing in the text, use null. Do not add fields or commentary. Text: [paste text]

A fixed schema and a null rule keep the output clean enough to use in code without extra parsing.

Reasoning with its work shown

Solve this step by step, then give a short final answer on its own line. If any step depends on an assumption, state the assumption. Problem: [paste problem]

It uses the model's reasoning strength while making the assumptions visible so you can check them.

Buying advice

Start free in the chat app

The web and mobile chat are free and enough to judge whether the answers fit your work before you write any code.

Use the API when you build, and start on the lighter model

Pay-per-token API access fits automated or high-volume work. Begin with the cheaper model and move up only when a task clearly needs it.

Self-host the open weights for data control

If sending data to the hosted service is a problem, run the open-weight models on your own hardware or a private host. This costs infrastructure and setup time in exchange for control.

Watchouts

  • The hosted service runs on servers subject to Chinese law. Do not send confidential or regulated data through it unless your policy and legal review allow it.
  • Cheap output is still not checked output. Verify facts and test code before you rely on it.
  • Model names and free-token terms change. Read the official pricing page before you commit a workload.
  • Content controls on the hosted chat can affect some topics. Self-hosting the open weights avoids that but shifts the work to you.

Best for

  • Getting strong reasoning and coding help without paying premium API rates
  • Running an open-weight model yourself when you need control over your data
  • Everyday chat and research through the free web app and mobile app

Not for

  • Teams that cannot send data to servers or models governed by Chinese data rules
  • Work where you will not check important facts or code before using it

How to use it well

Use the free chat app for daily questions and drafts. If you build with the API, start with V4 Flash and move to V4 Pro only when the task needs it. Keep repeated prompt prefixes identical so DeepSeek's automatic cache can reduce their cost.

Pricing note

Free chat app. V4 Flash and V4 Pro API rates change between off-peak and peak hours; the calculator uses the higher peak rate so it does not understate cost.

We link to DeepSeek API pricing instead of copying every price into this page. That is safer because AI tool pricing, usage limits, and plan names change often.

How to decide

Choose this if you want strong reasoning and coding help at the lowest cost, or an open-weight model you can run yourself.

Take the quizCheck costs

Use the calculator to compare DeepSeek API costs against other models before you move high-volume work onto it.

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