DeepSeek: from chat to getting work done
Open a free browser chat, feel deep reasoning and long context on a real task, then pick the web app, the DeepSeek API, or a tutorial.
- Works in the browser
- About 1M context
- OpenAI-compatible API
Three doors — chat, API, tutorials
Search results often push app-store downloads. The useful split here is different: try a conversation, wire a product, or learn with a guide. Pick the door that matches the job this week.
A four-step path that actually ships
Skip the download carousel. Use this order unless you already know you need an API key today.
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Open the web chat from the button above and send one real task — a messy email, a PDF question, or a code snippet you actually have.
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Decide from that reply: stay in the browser, or move the same instructions into the DeepSeek API with deepseek-v4-pro or deepseek-v4-flash.
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If you need an agent, point Deep Code, Harness, or Claude Code at the API. Do not download Hugging Face weights for that path.
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When a toggle looks like “expert / instant” or “thinking on/off”, treat it as a product control that can move. Confirm it in the live UI or API docs, not as a frozen contract on this page.
What you can do once a door is open
Deep reasoning, long context, files and vision are the same V4 family seen from different jobs. Each card links to a page that goes deeper without repeating the homepage stack.
Deep reasoning
Chain-of-thought on math, code and messy specs. Use it when a one-shot answer is not enough and you need the model to check itself. Compare Pro vs Flash on the features page.
V4 features →Long context
V4 Pro is built for about one million tokens — long reports, multi-file repos, and documents you would rather not split by hand. Confirm live limits on the Pro guide.
V4 Pro guide →Vision and files
Charts, UI shots, scans, PDFs and spreadsheets belong in the same conversation as text. The vision page shows what to upload and what still belongs in OCR or a parser.
Vision guide →Free chat path
The community web app is the try-then-decide door. It is not chat.deepseek.com. Use it to stabilize a prompt, then graduate to the API if you are shipping.
Web app guide →Jobs this stack is already used for
Eight starting scenes — each card is a real page on this site, not a decorative tag. Open the one that looks like your week.
Data work
Tables, Excel, and summaries through chat or the API.
Software
Code, reviews, and terminal agents on the same models.
Research
Long papers and ~1M context on V4 Pro.
Writing
Drafts and rewrites in the browser first.
Hard reasoning
Math, specs, and multi-step logic on the features page.
Product integration
OpenAI-compatible calls from your own app.
Learning path
Checklists from first chat to first API call.
Images
Charts, UI shots and scans with vision.
From answering questions to finishing tasks
A chatbot that only replies is a dead end if you actually need code written, tests run, or a repo patched. After a prompt is stable in the web app, point an agent shell at the same DeepSeek API: Deep Code in the terminal, DeepSeek Harness for files and commands, or Claude Code through the Anthropic-compatible endpoint. Those names are tools on the API, not new model IDs. Treat preview surfaces as documentation that can move.
How the engine is usually described
People search DeepSeek AI for the company, the Hugging Face org, and the product at once. Under the hood the live V4 line is a mixture-of-experts stack with multimodal inputs and a reasoning path you can turn up or down. This page does not replace the name-disambiguation guide: if you mixed the lab with a model string, open that page next.
Mixture of experts
Only some experts fire per token, which is how V4 keeps long context usable instead of lighting up every parameter.
Multimodal inputs
Text plus images (charts, shots, scans) in one request on Pro. Do not assume every Flash call sees pixels the same way.
Adaptive reasoning
Hard tasks get a longer thinking trace; everyday chat can stay fast. Confirm the live toggle in the app or API fields.
Related guides on this site
FAQ
How do I start for free in the browser?
Click Start chatting on this page. You land on the community web chat at app.deepseek.day. You do not need an API key for that first conversation. Official mobile apps are listed on DeepSeek’s own site and the real App Store / Google Play developer “杭州深度求索”; this page does not ship APKs.
What are the three doors?
Web chat to try a real task, the DeepSeek API to integrate a product, and tutorials when you want a checklist. They share the V4 family. They are not three download badges.
Do I need the DeepSeek API to chat?
No. Chat in the browser first. Create a key on the open platform only when you are calling from code or an agent shell.
Where do long context and vision live?
V4 Pro is the flagship for about 1M context and vision. V4 Flash is the faster, cheaper everyday tier. Confirm live IDs on the Pro / Flash guides and in the API docs.
How is this different from the homepage?
The homepage keeps the brand plus web entry, V4 Pro and free API. This page is the how-to-start conversion: deep reasoning, free chat, and three doors. Use it when you already know the brand and need a path.
Can I use Expert mode or Instant mode here?
Official chat and apps expose thinking / expert-style toggles that can change. On this site, start a web chat and use whatever reasoning control the live UI shows. Do not treat a screenshot from another domain as a switch on app.deepseek.day.
Where should I go after a good first reply?
Stay in the browser if that is enough. Move to the API if you are shipping. Open Deep Code, Harness or Claude Code if you need an agent. Fetch Hugging Face weights only for self-host or fine-tune.