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GPT-4o vs Claude Sonnet 4

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Compare GPT-4o and Claude Sonnet 4. Side-by-side features, pricing, and quality.

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Head-to-Head

GPT-4o Claude Sonnet 4
Provider OpenAI Anthropic
Category Chat Chat
Context window 128000 tokens 1000000 tokens
Cost per message Free.ai tokens (estimate) ~4781 tokens ~6750 tokens
Free to use without purchase? No — premium external model
Needs purchased tokens — $5 buys 200K		 No — premium external model
Needs purchased tokens — $5 buys 200K
Model page on Free.ai View GPT-4o → View Claude Sonnet 4 →
GPT-4o

OpenAI: GPT-4o is an AI model by OpenAI on Free.ai. It supports up to 128,000 tokens of context. Costs approximately 4,781 tokens per message. Try OpenAI: GPT-4o instantly — no sign up needed. Compare it side-by-side with other models.

Claude Sonnet 4

Anthropic: Claude Sonnet 4.6 is an AI model by Anthropic on Free.ai. It supports up to 1,000,000 tokens of context. Costs approximately 6,750 tokens per message. Try Anthropic: Claude Sonnet 4.6 instantly — no sign up needed. Compare it side-by-side with other models.

Which should you use?

Benchmarks can only tell you so much. The honest answer for any real workload is: send the same prompt to both and read the two answers yourself.

Free.ai's compare tool lets you do that in a single view, and the AI Arena collects community votes on blind responses if you want a broader signal.

Try GPT-4o and Claude Sonnet 4 side by side

Same prompt, two answers. Both are premium external models — use requires purchased tokens ($5 = 200K).

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Or try a free self-hosted model instead (Qwen, Mistral, DeepSeek, etc.) — no purchase needed.

FAQ

GPT-4o vs Claude Sonnet 4 is a side-by-side comparison of two AI models. GPT-4o is built by OpenAI, and Claude Sonnet 4 by Anthropic. Send them the same prompt at /chat/compare/ and read both answers side by side.

Not free — GPT-4o and Claude Sonnet 4 are premium external models routed through third-party providers, so they require purchased tokens (starting at $5 for 200,000 tokens). Only Free.ai's self-hosted open-source models like Qwen, Mistral, DeepSeek, FLUX, Kokoro, and Whisper are free to use without purchase.

Depends on your workload. Send the same prompt to both at /chat/compare/ and judge the two answers directly — benchmarks can only tell you so much. The AI Arena also collects community votes on blind responses if you want a broader signal.

Yes — GPT-4o and Claude Sonnet 4 are premium external models that need purchased tokens. You can create a free Free.ai account and buy tokens starting at $5 for 200K. Our self-hosted open-source models (Qwen, Mistral, DeepSeek, FLUX, Kokoro, Whisper, etc.) are free with an account and work without any purchase.

The compare tool sends the same prompt to GPT-4o and Claude Sonnet 4 in parallel and streams both responses side by side. Each panel has its own conversation history, so you can follow up differently on each side.

Yes. Each panel has its own model picker — change GPT-4o or Claude Sonnet 4 to any of 370+ models at any time. The conversation history on each side is preserved.

Free.ai bills in tokens, not per-message. A typical chat turn on GPT-4o uses about 4,781 Free.ai tokens per message; on Claude Sonnet 4, about 6,750 Free.ai tokens per message. $5 buys 200,000 tokens and they never expire. Self-hosted open-source models are free up to your daily allowance.

GPT-4o supports 128,000 tokens of context; Claude Sonnet 4 supports 1,000,000 tokens. Context window is how much text the model can read in a single conversation before older messages start being trimmed.

Yes. Signed-in users have their compare sessions saved automatically — see the sidebar on /chat/compare/ for past comparisons. Each comparison stores both sides (Model A and Model B) independently so you can revisit exact responses.

Only for external models. GPT-4o runs on OpenAI's servers (premium); your prompt is routed there through our external-model gateway when you use this pair. Self-hosted open-source models like Qwen, Mistral, DeepSeek, FLUX, Kokoro, and Whisper run on Free.ai's own GPUs — nothing leaves our infrastructure.

Yes. Both GPT-4o and Claude Sonnet 4 are accessible through the Free.ai API — one Bearer token, OpenAI-compatible chat/completions. Paid models require purchased tokens (no API access from the daily free pool).

Check the individual model pages — /apps/openai-gpt-4o/ and /apps/anthropic-claude-sonnet-4-6/ — for each model's specs. For head-to-head quality signal, look at the /arena/ leaderboard which ranks models by blind community votes. For your own workload, nothing beats sending the same prompts through the compare tool.

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