Claude Sonnet 5.5 vs DeepSeek V4 Flash
How Anthropic's Claude Sonnet 5.5 and DeepSeek's DeepSeek V4 Flash differ on paper, from the specs each provider publishes.
Compare them on your promptBoth answer side by side, free with your own API keys.
Key differences
- Both models accept 1M tokens of context.
- DeepSeek V4 Flash can write longer replies, up to 384K output tokens against 128K.
- Claude Sonnet 5.5 is the newer release (September 2026); DeepSeek V4 Flash came out in July 2026.
- Claude Sonnet 5.5 lists image input support that DeepSeek V4 Flash does not.
Side by side
| Spec | Claude Sonnet 5.5 | DeepSeek V4 Flash |
|---|---|---|
| Provider | Anthropic | DeepSeek |
| Released | September 2026 | July 2026 |
| Context window | 1M tokens | 1M tokens |
| Max output | 128K tokens | 384K tokens |
| Reasoning model | Yes | Yes |
| Price per 1M tokens (in / out) | $2 / $10 | See provider |
| Capabilities | Image input, Reasoning, Coding, Tool calling, Structured output, Extended thinking, Streaming | Reasoning, Coding, Tool calling, Structured output, Extended thinking, Streaming |
Specs as published by each provider. Benchmarks and output quality aren't covered here; the best test is your own prompts.
Specs only go so far. Ask both.
Send one message and get Claude Sonnet 5.5 and DeepSeek V4 Flash's answers side by side, with response time, tokens and cost for each. You'll need Anthropic and DeepSeek keys.
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