You want to try DeepSeek without touching a terminal, downloading 160 GB of weights, or filling in a credit-card form. Can you just open a browser tab and start talking to the same models developers pay for? Yes — and as of April 24, 2026, the version you reach when you use DeepSeek online is the brand-new V4 Preview, not the V3.2 model that powered the site through winter. This guide walks through every way to access DeepSeek from a browser or phone, what the new Expert Mode and Instant Mode toggles actually do, how the web chat differs from the developer API, and where the free online experience ends and paid billing begins.

The short answer: three ways to use DeepSeek online

There are three legitimate ways to reach DeepSeek from a browser or phone without installing model weights:

• The official web chat at chat.deepseek.com — free, account required, runs V4 by default.
• The official mobile app on iOS and Android — same account, same models, a mobile UI.
• The developer API at https://api.deepseek.com — pay-as-you-go, for building things on top of the models.

The first two are what most people mean by “DeepSeek online.” They’re interchangeable in terms of capability; the difference is form factor. The API is a separate surface with different rules, and I’ll cover it below because anyone building a product needs to understand how it behaves differently from the chat box.

What “DeepSeek online” runs today: V4 Preview

DeepSeek-V4 Preview is now available on web, app, and API following its release on April 24, 2026. On the web chat, V4 is exposed through two toggles:

• Expert Mode — routes to deepseek-v4-pro (1.6 trillion total parameters, 49 billion active). The frontier-tier model.
• Instant Mode — routes to deepseek-v4-flash (284 billion total, 13 billion active). Faster and cheaper, still on the new architecture.

V4 Preview launched on Hugging Face, the DeepSeek API, and chat.deepseek.com, with Expert Mode mapped to V4-Pro and Instant Mode to V4-Flash. Both models share a 1,000,000-token default context window with output up to 384,000 tokens, and both support a Thinking / Non-Thinking toggle (the DeepThink button) on top of the mode selector.

If you used DeepSeek online during the V3.x era, the DeepThink button is still there — it now switches V4 between non-thinking and thinking mode instead of switching models. The reading experience is the same; the model under the hood is newer.

Web chat vs mobile app vs API: the comparison table

The single most important row is conversation history. The web and app keep your chats on the server so you can scroll back through them; the API does not. If you build an app on top of the API, your server has to store the conversation and resend it with every call — I’ll come back to this.

Signing in to the official web chat

To use DeepSeek online the way most readers mean the phrase:

1. Go to https://chat.deepseek.com in any modern browser. DeepSeek’s own description is that the chat supports coding, content creation, file reading, document upload, and long-context conversations.
2. Click Sign up or Log in. You can register with an email address, a phone number (where supported), or a single-sign-on provider.
3. Verify the account and you’re in.
4. In the prompt bar, pick Instant Mode for fast replies or Expert Mode when you want the bigger model. Toggle DeepThink when you want the model to reason step by step before answering.

If you have an older account that predates V4, no migration is needed. The same login works, and the model selector has just been replaced with the two new modes. For a walkthrough of the full account flow, see our dedicated sign up for DeepSeek guide.

What you get for free — and what’s not documented

Normal browser use of the chat is free. You do not need a credit card to open an account, and there is no paid tier inside the web app itself. I tested both modes across a week of my own coding and research sessions, and Expert Mode held up on a 400-page PDF uploaded into a single prompt without losing the thread.

Two things I won’t claim, because DeepSeek does not publicly document them:

• A specific daily message cap. DeepSeek does not publish one as of April 2026. Heavy users sometimes see fair-use slowdowns; the exact thresholds are not printed on the site.
• A guaranteed uptime number. For production work, check the DeepSeek status checker before assuming the chat is up in your region.

For a fuller treatment of the free-versus-paid split, read DeepSeek free vs paid.

Where the web chat ends and the API begins

When people ask about “DeepSeek online” in a developer context, they usually mean the API. It runs over POST /chat/completions, the OpenAI-compatible endpoint hosted at https://api.deepseek.com. The API supports both OpenAI ChatCompletions and Anthropic API formats, and both V4 models support 1M context with dual Thinking / Non-Thinking modes.

The smallest working Python example looks like this:

from openai import OpenAI

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

resp = client.chat.completions.create(
    model="deepseek-v4-flash",
    messages=[{"role": "user", "content": "Summarise this quarter's report."}],
    temperature=1.0,
    max_tokens=2048,
)
print(resp.choices[0].message.content)

To turn on thinking mode, add reasoning_effort="high" and extra_body={"thinking": {"type": "enabled"}}. The response then carries reasoning_content alongside the final content. Useful parameters to know: temperature, top_p, max_tokens, reasoning_effort, plus JSON mode, tool calling, and streaming. Our DeepSeek API getting started guide covers these end to end.

Four things change when you move from the web chat to the API:

1. Statelessness. The API does not remember your previous turns. Every request must include the full messages array. The web chat does this for you; the API does not.
2. Billing. You pay per token. No free tier in the API beyond whatever promotional granted balance may be in your billing console.
3. Legacy IDs. The legacy model IDs deepseek-chat and deepseek-reasoner will be fully retired and inaccessible after July 24, 2026, 15:59 UTC, and currently route to deepseek-v4-flash in non-thinking and thinking modes respectively. Migrating is a one-line model= swap; the base URL does not change.
4. JSON mode. Set response_format={"type": "json_object"}. It is designed to return valid JSON rather than guaranteed to; the prompt should include the word “json” plus a small example schema, and max_tokens should be high enough to avoid truncation.

What a real month costs on the API

Say you build a customer-support bot on top of DeepSeek online, running 1,000,000 requests a month with a 2,000-token cached system prompt, a 200-token user message, and a 300-token reply. On deepseek-v4-flash:

• Cached input: 2,000 × 1,000,000 tokens × $0.028/M = $56.00
• Uncached input: 200 × 1,000,000 tokens × $0.14/M = $28.00
• Output: 300 × 1,000,000 tokens × $0.28/M = $84.00
• Total: $168.00

The same workload on deepseek-v4-pro costs $290 + $348 + $1,044 = $1,682.00, roughly ten times the Flash bill. Pro earns its keep when the quality lift on agentic or competitive-programming-style tasks pays for the gap; for everyday chat, Flash is the default. DeepSeek’s pricing page lists $0.14 per million input tokens and $0.28 per million output for Flash, and $1.74 per million input and $3.48 per million output for Pro as of April 2026 — verify current numbers on DeepSeek API pricing before committing. A light promotional granted balance may be visible in your billing console; do not plan around it.

Country and platform notes

Using DeepSeek online from the US, UK, Canada, Australia, New Zealand, or Ireland generally works without a VPN. Some exceptions to know:

• Italy’s Garante ordered blocking of the DeepSeek app in January 2025 over data-protection concerns, and multiple US states, Australia, Taiwan, South Korea, Denmark and Italy introduced bans or other restrictions on DeepSeek-R1 shortly after its release, citing privacy and national security concerns.
• Several US states restrict DeepSeek on government-issued devices. There is no federal consumer ban at the time of writing.
• Conversations are processed on servers subject to Chinese law. Treat prompts, uploaded files, and chat history as you would any third-party cloud service. Our DeepSeek privacy page covers the trade-offs in detail.

For the country-by-country picture, see DeepSeek availability by country.

Browser vs app: which should you use?

For typing long prompts, uploading PDFs, or working with code blocks, the browser at chat.deepseek.com is better. Copy-paste is easier, the layout uses your full screen, and keyboard shortcuts work. For quick questions while walking or in meetings, the mobile app is fine. Both sync conversation history to the same account, so you can start on your phone and finish on a laptop. If you want a deeper comparison, read DeepSeek browser vs app.

One piece of advice: if you see a third-party site advertising “DeepSeek online — no login, no limits,” treat it with skepticism. These sites are usually proxies; your prompts leave your machine, pass through a third party you have no contract with, and then may or may not reach DeepSeek. For anything with real data, use chat.deepseek.com or the API directly.

When DeepSeek online is not the right choice

Honest weaknesses after a month of use on V4 Preview:

• Real-time web browsing is limited compared to integrated-search competitors. The chat can use a search tool when enabled, but it is not a full research agent.
• Image generation is not part of the chat at V4 Preview. DeepSeek has separate vision work (Janus, VL2), but the default chat UI does not draw pictures for you.
• Regulated-data workloads — medical records, legal discovery, financial PII — need private deployment. For those, see install DeepSeek locally or pick a provider that contracts on your jurisdiction.

If any of those apply, the right fix is not a different chat URL but a different access pattern: self-hosted weights, a regional API provider, or a competitor with a residency contract that suits you. Our DeepSeek beginner guides hub collects the further reading you’ll need.

Last verified: 2026-04-24. DeepSeek AI Guide is an independent resource and is not affiliated with DeepSeek or its parent company. Model IDs, pricing and API behaviour change; check the official DeepSeek documentation and pricing page before committing to a production decision.