DeepSeek review

What DeepSeek is

DeepSeek is an AI research company based in Hangzhou, China. It became widely known in early 2025 when its R1 reasoning model rivaled leading Western models at a fraction of the training and usage cost. Today it offers three things: a free chat assistant (web, iOS and Android), the DeepSeek Harness desktop app, and the DeepSeek API for developers.

In September 2026 DeepSeek introduced DeepSeek-V4.1-Flash, the smallest model in a new architecture family with native visual understanding. DeepSeek says multiple tests put it ahead of its own V4-Pro on performance, cost and speed, so V4-Pro requests now route to V4.1-Flash until V4.1-Pro launches.

Key features

Free chat assistant

Ask questions, write, code and analyze documents for free in the web or mobile app.

V4.1-Flash model

A new causal encoder-decoder design with just 8B active parameters for input and 16B for output, plus a much smaller KV cache that DeepSeek says cuts cache-hit costs for agents.

Long context and thinking mode

1M-token context, up to 384K output tokens, and both thinking (default) and non-thinking modes.

Developer-friendly API

JSON output, tool calls, a Responses API, chat prefix and fill-in-the-middle completion (beta), and both OpenAI- and Anthropic-format base URLs.

Agent integrations

DeepSeek’s docs list setups for Claude Code, Codex, OpenCode and other coding agents.

Pricing breakdown

From DeepSeek’s API docs, checked October 16, 2026 (per 1M tokens, USD). Prices took effect September 10, 2026.

deepseek-flash (V4.1-Flash)	Off-peak	Peak
Input, cache hit	$0.003	$0.006
Input, cache miss	$0.15	$0.30
Output	$0.60	$1.20

Peak hours are 01:00–04:00 and 06:00–10:00 UTC on weekdays (excluding Chinese public holidays). Charges deduct from a prepaid balance, using any granted balance first. The chat app is free.

Best use cases

• High-volume API tasks: classify or summarize thousands of support tickets for a few dollars.
• Coding agents: point a compatible coding agent at DeepSeek’s Anthropic-format endpoint to cut costs.
• Long documents: analyze very long reports or codebases within the 1M-token context.
• Everyday chat: use the free app for explanations, drafts and brainstorming.

How to get started

1. Use the free chat at deepseek.com or download the app.
2. For the API, create an account on the DeepSeek Platform and top up a balance.
3. Create an API key and set the base URL to https://api.deepseek.com (or the /anthropic endpoint).
4. Use the model name deepseek-flash.
5. Schedule large batch jobs during off-peak hours to halve costs.
6. Check DeepSeek’s change log regularly, as models are retired quickly.

Tips and tricks

• Use context caching: repeated prompt prefixes hit the cache at a tiny fraction of the cost.
• Switch thinking mode off for simple tasks to reduce output tokens.
• Review your data policies before sending sensitive information.
• Keep a fallback model in your app in case of model changes or outages.

Example API system prompt:

You are a support ticket classifier. Return JSON with fields “category” (billing, bug, how-to, feature-request), “urgency” (low, medium, high) and a one-sentence “summary.” Do not include any other text.

Pros and cons

👍 Pros

• Free chat app
• Extremely low API prices, with 50% off-peak discounts
• Large 1M-token context window
• Drop-in compatible with OpenAI and Anthropic API formats
• Supports popular coding agents like Claude Code, Codex and OpenCode

👎 Cons

• China-based company, which matters for some data and compliance policies
• Model lineup changes quickly (V4-Pro is being phased out)
• Fewer consumer features (image generation, voice) than ChatGPT or Gemini
• Peak-hour pricing requires planning for cost-sensitive jobs

Who should (and shouldn't) use DeepSeek

✅ A good fit if you…

• Build apps or agents where API cost matters most
• Want a capable free chatbot for general questions
• Run batch jobs you can schedule off-peak

⛔ Look elsewhere if you…

• Work under policies that restrict China-based data processing
• Need an all-in-one assistant with images, voice and video
• Need long-term model stability without migrations

DeepSeek alternatives

• ChatGPT — OpenAI's AI assistant for chat, research, writing, coding, images, voice and agentic work. (from $8/mo (Go); Plus $20; Pro $100–$500)
• Claude — Anthropic's AI assistant for writing, analysis, research, coding and long-running work, with Claude Code included on paid plans. (from $17/mo (Pro, annual; $20 monthly); Max from $100)
• Google Gemini — Google's AI assistant for chat, research, image and video generation, built into Gmail, Docs and Android. (from $4.99/mo (Google AI Plus))
• Mistral Vibe (formerly Le Chat) — Mistral's AI assistant and coding agent in one product—Le Chat is now Vibe. (from $14.99/mo (Pro, excluding taxes))
• Grok — xAI's AI assistant for chat, real-time answers and image and video creation, sold through The X Subscription. (from $8/mo (Plus) or $80/yr)

FAQ

Is DeepSeek free?

Yes. DeepSeek's chat assistant is free on the web and mobile apps. The API is paid per token.

How much does the DeepSeek API cost?

For deepseek-flash (DeepSeek-V4.1-Flash), DeepSeek lists $0.30 per 1M input tokens (cache miss), $0.006 (cache hit) and $1.20 per 1M output tokens at peak. Off-peak rates are half: $0.15, $0.003 and $0.60.

When are DeepSeek's off-peak hours?

Peak hours are 01:00–04:00 and 06:00–10:00 UTC, Monday to Friday, excluding Chinese public holidays. All other times, including weekends, are off-peak.

What is DeepSeek-V4.1-Flash?

It's DeepSeek's newest model, announced in September 2026, with a new encoder-decoder architecture, native visual understanding, a 1M-token context and both thinking and non-thinking modes.

Can I use DeepSeek with Claude Code or the OpenAI SDK?

Yes. DeepSeek offers OpenAI-format and Anthropic-format endpoints, and its docs list integrations with Claude Code, Codex, OpenCode and others.

Sources

This is an editorial review based on research of official DeepSeek pages and documentation, not hands-on benchmark testing. Prices are in USD and were checked on October 16, 2026; vendors change plans often, so confirm on the official pricing page before buying.

1. DeepSeek API docs: Models & Pricing
2. DeepSeek news: Introducing DeepSeek-V4.1-Flash
3. DeepSeek homepage