DeepSeek V4.1 Flash vs DeepSeek V4 Flash
Pricing, context window and real answers (September 2026)
DeepSeek V4.1 Flash (DeepSeek) and DeepSeek V4 Flash (DeepSeek), compared as you can actually call them on FastMetal. Both are served from the same OpenAI-compatible endpoint and API key; switching is a change to the model string.
Specs and pricing
 DeepSeek V4.1 Flash | DeepSeek V4 Flash | |
|---|---|---|
| Provider | DeepSeek | DeepSeek |
| Input (per 1M tokens) | ¥50.69 | ¥22.85 |
| Output (per 1M tokens) | ¥202.74 | ¥49.21 |
| Typical cost (1,000 in + 500 out tokens × 1,000 calls) | ¥152 | ¥47 |
| Context window | 1,048,576 tokens | 1,048,576 tokens |
| Release date | 9/10/2026 | 4/24/2026 |
| Input modalities | text, image | text |
| Arena · overall | Unranked | #91 · ELO 1,436 |
| Arena · Japanese | Unranked | #75 · ELO 1,397 |
| Arena · coding | Unranked | #90 · ELO 1,483 |
Prices are FastMetal's yen rates before tax. Arena ranks are as of the latest leaderboard scrape.
Which should you pick?
- On price, DeepSeek V4 Flash: ¥49.21 per 1M output tokens, 76% less than DeepSeek V4.1 Flash.
- If in doubt, try both on the same key. Switching is a change to the model string, and each is billed at its own rate.
Real answers to the same prompts
Exactly what the FastMetal gateway returned, side by side. Not benchmark scores: actual output.
Count the number of 'r's in 'strawberry'
Count the number of 'r's in 'strawberry'. Explain your reasoning step by step.
DeepSeek V4.1 Flash
The word **“strawberry”** has **3** letter **“r”**s.
Step-by-step:
1. Spell it out: **s t r a w b e r r y**
2. Find each **r**:
- Position 3: **r** in “str”
- Position 8: first **r** in “berry”
- Position 9: second **r** in “berry”
3. Total: **3**
**Answer: 3**
7.5s226 output tokens
DeepSeek V4 Flash
The word "strawberry" is spelled as s-t-r-a-w-b-e-r-r-y. I go through each letter: s (no), t (no), r (yes, first), a (no), w (no), b (no), e (no), r (yes, second), r (yes, third), y (no). Thus, there are three 'r's.
3.9s251 output tokens
Debug This Error
I'm getting the following error in my Node.js application: TypeError: Cannot read properties of undefined (reading 'map') at UserList (/app/components/UserList.js:12:25) at renderWithHooks (/app/node_modules/rea…
DeepSeek V4.1 Flash
The error means that `users` is `undefined` when `UserList` renders, so JavaScript cannot call `.map()` on it.
Your component expects a `users` prop:
```jsx
function UserList({ users }) {
return (
<ul>
{users.map(user => <li key={user.id}>{user.name}</li>)}
</ul>
);
}
```
But it is being rendered without `users`, or `users` has not loaded yet.
Common causes:
1. Parent renders it without the prop:
```jsx
<UserList />
```
instead of:
```jsx
<UserList users={users} />
```
2. The prop name is different:
```jsx
<UserList userList={users} />
```
3. The data is fetched asynchronously and is initially `undefined`:
```jsx
const [users, setUsers] = useState();
useEffect(…
16.0s945 output tokens
DeepSeek V4 Flash
The error occurs because `users` is `undefined` when the component tries to call `.map()` on it.
## Why this happens
Your component expects `users` to be an array, but it's receiving `undefined` as a prop. This typically happens when:
1. The parent component doesn't pass the `users` prop
2. The data fetching hasn't completed yet (async data loading)
3. The API response is missing the expected data structure
## How to fix it
### Option 1: Default prop value (Recommended for initial state)
```jsx
function UserList({ users = [] }) {
return (
<ul>
{users.map(user => <li key={user.id}>{user.name}</li>)}
</ul>
);
}
```
### Option 2: Guard clause (More explicit)
```jsx
func…
6.3s422 output tokens
Code Review
Please review the following Python function and suggest improvements for readability, performance, and best practices: def get_data(url, retries=3): import requests import time for i in range(retries):…
DeepSeek V4.1 Flash
Here are the main improvements:
- Move imports to module level.
- Avoid bare `except`; catch specific exceptions.
- Use a `requests.Session` for connection reuse.
- Retry only transient network/HTTP failures, not all errors.
- Use exponential backoff and don’t sleep after the final attempt.
- Use a list comprehension for readability/performance.
- Add type hints, logging, constants, and basic JSON validation.
- Avoid `== True`; use `is True` or a truthy check depending on API contract.
Example refactor:
```python
from __future__ import annotations
import logging
import time
from typing import Any
import requests
logger = logging.getLogger(__name__)
TIMEOUT = (3.05, 10) # connect time…
31.5s5142 output tokens
DeepSeek V4 Flash
Here's a comprehensive review with suggested improvements:
## Issues Identified:
1. **Import at wrong location** - Imports inside functions are inefficient and non-standard
2. **Bare `except:` clause** - Catches all exceptions including `KeyboardInterrupt`, `SystemExit`
3. **Missing error handling granularity** - Should distinguish between retryable and non-retryable errors
4. **Duplicate sleep logic** - Same sleep in `else` and `except` blocks
5. **Unnecessary variable** - `data` is only used once
6. **Inefficient list building** - Manual loop instead of list comprehension
7. **Hardcoded error message** - No logging or error context
8. **Missing type hints** - No type annotations
9. **Fun…
12.6s987 output tokens
Frequently asked questions
- Which is cheaper, DeepSeek V4.1 Flash or DeepSeek V4 Flash?
- Per 1M output tokens, DeepSeek V4.1 Flash is ¥202.74 and DeepSeek V4 Flash is ¥49.21 on FastMetal (yen, before tax), so DeepSeek V4 Flash is cheaper.
- How do the context windows of DeepSeek V4.1 Flash and DeepSeek V4 Flash compare?
- DeepSeek V4.1 Flash takes 1,048,576 tokens; DeepSeek V4 Flash takes 1,048,576.
- Can I use DeepSeek V4.1 Flash and DeepSeek V4 Flash with the same API key?
- Yes. On FastMetal's OpenAI-compatible endpoint, switch by passing "deepseek-v4.1-flash" or "deepseek-v4-flash" as the model. Each is billed at its own rate from the same prepaid balance.
Try both on one API key
Create an account and add credit to call DeepSeek V4.1 Flash and DeepSeek V4 Flash from the browser chat and the API. No monthly fee.