Yeschat

DeepSeek R1 Online: Now DeepSeek V4.1 Flash

For problems that need real reasoning, math, logic or tricky code, use DeepSeek V4.1 Flash with thinking mode on and get the answer worked out step by step.

What Is DeepSeek-R1?

DeepSeek-R1 is DeepSeek's reasoning model, released on January 20, 2025. On YesChat it has been replaced by DeepSeek V4.1 Flash, DeepSeek's newer chat model (released on September 10, 2026). With the Thinkdeep switch on, DeepSeek V4.1 Flash works through a problem before answering, which takes longer than a direct answer. It is in the chat on the Pro plan and above. YesChat is not a DeepSeek product.

What Thinking Mode Is Good For

Math with every step

Ask it to solve a problem and show each step; then ask why a step holds. Useful for checking your own solution.

Logic puzzles and tricky questions

Questions with traps, several conditions or a chain of "if… then…" are where a reasoning model helps most.

Debugging code

Paste the code and the error and ask it to find the cause; it walks through what the code does before suggesting a fix.

Planning and trade-offs

Compare options with their pros and cons, or break a big task into ordered steps.

Thinking Mode or Direct Answers?

Use thinking mode when a question needs detailed step-by-step reasoning; for direct answers to everyday questions, turn it off or switch to another chat model on YesChat, such as GPT-5.6 Luna, Gemini 3.1 Pro or Claude Sonnet 5.

Thinking on for hard problems

Slower, because the model reasons first, and better on math, logic and debugging.

Thinking off for everyday questions

With Thinkdeep off, DeepSeek V4.1 Flash answers directly, for drafts, explanations and quick code help. More on the model on the DeepSeek chat page.

Other models in the same chat

Compare DeepSeek V4.1 Flash with Gemini 3.1 Pro or Claude Sonnet 5 on the same question.

How to Get Step-by-Step Reasoning on YesChat

  • Sign in to YesChat

    Sign up for a free YesChat account or sign in. DeepSeek V4.1 Flash is on the Pro plan and above.

  • Open DeepSeek V4.1 Flash and turn on Thinkdeep

    Click "Chat with DeepSeek V4.1 Flash in YesChat": the YesChat chat opens with DeepSeek V4.1 Flash selected. Turn on Thinkdeep, then give it the whole problem: all numbers, conditions and what counts as the answer. It needs the Pro plan or higher; a free account can use GPT-5.6 Luna.

  • Ask for the reasoning

    Ask for the steps, not just the result, and check the reasoning before you rely on it.

Frequently Asked Questions