Which is cheaper, DeepSeek V4.1 Flash and GPT-5.5?

DeepSeek V4.1 Flash has the lowest input price. Per 1M input tokens: DeepSeek V4.1 Flash from $0.20 and GPT-5.5 from $5.50.

Which has the larger context window, DeepSeek V4.1 Flash and GPT-5.5?

GPT-5.5 has the largest context window: DeepSeek V4.1 Flash 1,048,576 tokens and GPT-5.5 1,050,000 tokens.

Can I switch between DeepSeek V4.1 Flash and GPT-5.5 without changing my code?

Yes. All of them are served through FastRouter's OpenAI-compatible API, so switching is a change of the model parameter (deepseek/deepseek-v4.1-flash, openai/gpt-5.5).

DeepSeek V4.1 Flash vs GPT-5.5

Side-by-side pricing per provider, context window, benchmark scores and speed, all on one OpenAI-compatible API.

DeepSeek V4.1 Flash DeepSeekdeepseek/deepseek-v4.1-flash

GPT-5.5 OpenAIopenai/gpt-5.5

Creator

DeepSeek

OpenAI

Released

Sep 14, 2026

Apr 24, 2026

Context window

1.05M

Max output

944K

128K

Input / 1MLowest provider price

$0.20$0.20–$0.30 across 5

$5.50

Output / 1MLowest provider price

$0.60$0.60–$1.20 across 5

$33.00

Providers

IntelligenceArtificial Analysis index

39.5

38.4

CodingArtificial Analysis index

—

74.9

LatencyMedian time to first token

—

6.1s

ThroughputMedian tokens per second

—

<1 t/s

Accepts

Text, Image

Files, Image, Text

Produces

Text

Tool calling

Yes

Structured output

Yes

Reasoning

Yes

DeepSeek V4.1 Flash vs GPT-5.5: summary

DeepSeek V4.1 Flash and GPT-5.5 are both available through FastRouter's OpenAI-compatible API, so switching between them is a change of model id, not a new integration.

DeepSeek V4.1 Flash, from DeepSeek, has a 1,048,576-token context window, costs from $0.20/1M input and $0.60/1M output tokens across 5 providers and scores 39.5 on the Artificial Analysis Intelligence Index.

GPT-5.5, from OpenAI, has a 1,050,000-token context window, costs from $5.50/1M input and $33.00/1M output tokens across 2 providers and scores 38.4 on the Artificial Analysis Intelligence Index.

DeepSeek V4.1 Flash is the cheapest on input, 28× cheaper than the next model, GPT-5.5 has the largest context window and DeepSeek V4.1 Flash scores highest for intelligence.

Switch with one line

client = OpenAI(base_url="https://api.fastrouter.ai/api/v1", api_key="<FASTROUTER_API_KEY>") client.chat.completions.create(model="deepseek/deepseek-v4.1-flash", messages=[...]) # or client.chat.completions.create(model="openai/gpt-5.5", messages=[...])

Full API docs

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Benchmark scores sourced from ArtificialAnalysis