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Claude Sonnet 5.5 vs DeepSeek-V4-Flash-0423

Claude Sonnet 5.5 leads the LLM Stats Score 58.0 to 36.0. DeepSeek-V4-Flash-0423 is 35.6x cheaper per token.

Anthropic · DeepSeek · Updated for 2026

Which is better?

Claude Sonnet 5.5 leads the overall LLM Stats Score 58.0 to 36.0, ranking #3 overall.

In the 2 individual benchmarks reported for both models, Claude Sonnet 5.5 wins 2; this is a narrower head-to-head signal than the composite indexes.

On price, DeepSeek-V4-Flash-0423 is roughly 35.6x cheaper per token on a blended 3:1 input/output basis, which adds up quickly at production volume.

DeepSeek-V4-Flash-0423 also accepts a larger context window (1,048,576 input tokens), making it the stronger choice for long documents and large codebases.

Based on current LLM Stats indexes, shared benchmarks, pricing, and model metadata for 2026.

Choose Claude Sonnet 5.5

  • overall performance matters — it scores 58.0 and ranks #3 on LLM Stats
  • your work emphasizes reasoning and coding — it leads those capability indexes
  • you value its reported benchmark strengths — it wins 2 of 2 exact shared results
  • you want the most recent training data — it shipped Sep 2026

Choose DeepSeek-V4-Flash-0423

  • cost matters — it's about 35.6x cheaper per token
  • you process long inputs — it offers a 1,048,576 token context window
  • you need open weights you can self-host or fine-tune

At a glance

The differences that matter most.

Claude Sonnet 5.5
Anthropic
DeepSeek-V4-Flash-0423
DeepSeek
Core performance indexes
LLM Stats Score
58.0
#3
36.0
#89
Reasoning
56.6
#3
37.0
#79
Coding
48.8
#2
26.6
#71
Agents
42.3
#3
15.6
#90
Cost, coverage & limits
Benchmark wins
2 of 2
0 of 2
Input price
$2.00 / M
$0.09 / M
Output price
$10.00 / M
$0.18 / M
Context window
1,000,000
1,048,576

Capability indexes

Additional strengths measured across groups of related public benchmarks

2 shared
Index
Claude Sonnet 5.5
DeepSeek-V4-Flash-0423
Math
36.9#34
36.8#35
Tool use
34.0#2
15.4#92
Conservative TrueSkill rating · higher is betterHow scores work

Individual benchmarks

47 reported for Claude Sonnet 5.5 · 19 for DeepSeek-V4-Flash-0423

2 shared

Claude Sonnet 5.5 outperforms in 2 benchmarks (SWE-bench Multilingual, SWE-Bench Pro), while DeepSeek-V4-Flash-0423 is better at 0 benchmarks.

Claude Sonnet 5.5 significantly outperforms across most benchmarks.

Fri Oct 02 2026 • llm-stats.com

Human preference

Blind head-to-head votes and playground preference scores

Pricing Analysis

Price comparison per million tokens

DeepSeek-V4-Flash-0423 costs less

For input processing, Claude Sonnet 5.5 ($2.00/1M tokens) is 22.2x more expensive than DeepSeek-V4-Flash-0423 ($0.09/1M tokens).

For output processing, Claude Sonnet 5.5 ($10.00/1M tokens) is 55.6x more expensive than DeepSeek-V4-Flash-0423 ($0.18/1M tokens).

In conclusion, Claude Sonnet 5.5 is more expensive than DeepSeek-V4-Flash-0423.*

* Using a 3:1 ratio of input to output tokens

Lowest available price from all providers
Fri Oct 02 2026 • llm-stats.com
Anthropic
Claude Sonnet 5.5
Input tokens$2.00
Output tokens$10.00
Best providerAnthropic
DeepSeek
DeepSeek-V4-Flash-0423
Input tokens$0.09
Output tokens$0.18
Best providerDeepinfra
Notice missing or incorrect data?

Context Window

Maximum input and output token capacity

DeepSeek-V4-Flash-0423 accepts 1,048,576 input tokens compared to Claude Sonnet 5.5's 1,000,000 tokens. DeepSeek-V4-Flash-0423 can generate longer responses up to 1,048,576 tokens, while Claude Sonnet 5.5 is limited to 128,000 tokens.

Anthropic
Claude Sonnet 5.5
Input1,000,000 tokens
Output128,000 tokens
DeepSeek
DeepSeek-V4-Flash-0423
Input1,048,576 tokens
Output1,048,576 tokens
Fri Oct 02 2026 • llm-stats.com

Input capabilities

Documented input modalities across available providers

Claude Sonnet 5.5 supports multimodal inputs, whereas DeepSeek-V4-Flash-0423 does not.

Claude Sonnet 5.5 can handle both text and other forms of data like images, making it suitable for multimodal applications.

Claude Sonnet 5.5

Text
Images
Audio
Video

DeepSeek-V4-Flash-0423

Text
Images
Audio
Video

License

Usage and distribution terms

Claude Sonnet 5.5 is licensed under a proprietary license, while DeepSeek-V4-Flash-0423 uses MIT.

License differences may affect how you can use these models in commercial or open-source projects.

Claude Sonnet 5.5

Proprietary

Closed source

DeepSeek-V4-Flash-0423

MIT

Open weights

Release Timeline

When each model was launched

Claude Sonnet 5.5 was released on 2026-09-28, while DeepSeek-V4-Flash-0423 was released on 2026-04-23.

Claude Sonnet 5.5 is 5 months newer than DeepSeek-V4-Flash-0423.

Claude Sonnet 5.5

Sep 28, 2026

3 days ago

5mo newer
DeepSeek-V4-Flash-0423

Apr 23, 2026

5 months ago

Knowledge Cutoff

When training data ends

Claude Sonnet 5.5 has a documented knowledge cutoff of 2026-06-01, while DeepSeek-V4-Flash-0423's cutoff date is not specified.

We can confirm Claude Sonnet 5.5's training data extends to 2026-06-01, but cannot make a direct comparison without DeepSeek-V4-Flash-0423's cutoff date.

Claude Sonnet 5.5

Jun 2026

DeepSeek-V4-Flash-0423

—

Provider Availability

Claude Sonnet 5.5 is available from Anthropic. DeepSeek-V4-Flash-0423 is available from DeepInfra, Novita.

Claude Sonnet 5.5

anthropic logo
Anthropic
Input Price:Input: $2.00/1MOutput Price:Output: $10.00/1M

DeepSeek-V4-Flash-0423

deepinfra logo
Deepinfra
Input Price:Input: $0.09/1MOutput Price:Output: $0.18/1M
novita logo
Novita
Input Price:Input: $0.14/1MOutput Price:Output: $0.28/1M
* Prices shown are per million tokens

Outputs Comparison

Notice missing or incorrect data?

Judge for yourself.

Run your own prompts against Claude Sonnet 5.5 and DeepSeek-V4-Flash-0423 side-by-side, then vote on the output you prefer.

Claude Sonnet 5.5
✓ Preferred
DeepSeek-V4-Flash-0423
Open in Playground

FAQ

Common questions about Claude Sonnet 5.5 vs DeepSeek-V4-Flash-0423.

Which is better, Claude Sonnet 5.5 or DeepSeek-V4-Flash-0423?

Claude Sonnet 5.5 leads the LLM Stats Score 58.0 to 36.0. Claude Sonnet 5.5 is made by Anthropic and DeepSeek-V4-Flash-0423 is made by DeepSeek. The best choice depends on your use case — compare their capability indexes, individual benchmarks, pricing, and limits above.

How does Claude Sonnet 5.5 compare to DeepSeek-V4-Flash-0423 in benchmarks?

Claude Sonnet 5.5 scores BenchCAD (with Python tool): 96.3%, ArXivMath (with tools): 95.2%, Global-MMLU: 92.1%, MILU: 91.6%, SWE-bench Multilingual: 90.3%. DeepSeek-V4-Flash-0423 scores CodeForces: 93.9%, HMMT Feb 26: 91.9%, LiveCodeBench: 88.4%, GPQA: 87.4%, MMLU-Pro: 86.4%.

Is Claude Sonnet 5.5 cheaper than DeepSeek-V4-Flash-0423?

DeepSeek-V4-Flash-0423 is 22.2x cheaper for input tokens. Claude Sonnet 5.5 costs $2.00/M input and $10.00/M output via anthropic. DeepSeek-V4-Flash-0423 costs $0.09/M input and $0.18/M output via deepinfra.

What are the context window sizes for Claude Sonnet 5.5 and DeepSeek-V4-Flash-0423?

Claude Sonnet 5.5 supports 1.0M tokens and DeepSeek-V4-Flash-0423 supports 1.0M tokens. A larger context window lets you process longer documents, conversations, or codebases in a single request.

What are the main differences between Claude Sonnet 5.5 and DeepSeek-V4-Flash-0423?

Key differences include LLM Stats Score (58.0 vs 36.0), context window (1.0M vs 1.0M), input pricing ($2.00 vs $0.09/M), multimodal support (yes vs no), licensing (Proprietary vs MIT). See the full comparison above for benchmark-by-benchmark results.

Who makes Claude Sonnet 5.5 and DeepSeek-V4-Flash-0423?

Claude Sonnet 5.5 is developed by Anthropic and DeepSeek-V4-Flash-0423 is developed by DeepSeek.

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