# OpenAI o3 vs Claude Opus 4.8

> Markdown mirror of https://router.one/models/compare/o3-vs-claude-opus-4-8 for AI assistants and crawlers. Router One is an OpenAI-compatible LLM API gateway.

Claude Opus 4.8 is the lower-priced of the two on Router One — about 10% less on a 1M-input + 1M-output mix. OpenAI o3 offers 200K of context vs 1.05M for Claude Opus 4.8. OpenAI o3 answers on /v1/chat/completions and /v1/responses (Codex CLI); Claude Opus 4.8 on /v1/chat/completions and /v1/messages (Claude Code).

OpenAI o3 and Claude Opus 4.8 compared on current per-token rates, context window, and capabilities — both callable through one OpenAI-compatible endpoint with per-request cost traces.

## OpenAI o3 vs Claude Opus 4.8: rates, context window, and capabilities

| Spec | OpenAI o3 | Claude Opus 4.8 |
| --- | --- | --- |
| Input / 1M tokens | $3.00 | $2.25 |
| Output / 1M tokens | $12.00 | $11.25 |
| Cached input / 1M tokens | $3.00 | $0.375 |
| Context window | 200K | 1.05M |
| Capabilities | Chat, Streaming, Tool calling, Vision | Chat, Streaming, Tool calling, Vision |
| Detail page | [OpenAI o3](https://router.one/models/o3) | [Claude Opus 4.8](https://router.one/models/claude-opus-4-8) |

## What does 1M tokens cost on OpenAI o3 vs Claude Opus 4.8?

For a workload of 1M input plus 1M output tokens at current rates: OpenAI o3 comes to $15.00, Claude Opus 4.8 comes to $13.50 — Claude Opus 4.8 is about 10% cheaper on this mix. Real workloads skew heavily toward input tokens, so weigh the input rate by your own ratio; the cached-input row above is the posted catalog rate for that model.

## Switch between OpenAI o3 and Claude Opus 4.8 without changing code

Both models are behind the same OpenAI-compatible endpoint, so an A/B test is a one-string change — same key, same code, and every request traced with tokens, cost, and latency in the dashboard:

`compare.sh`

```bash
curl https://api.router.one/v1/chat/completions \
  -H "Authorization: Bearer sk-your-router-one-key" \
  -H "Content-Type: application/json" \
  -d '{"model": "openai/o3", "messages": [{"role": "user", "content": "Hello"}]}'

# Same request, other model — change one string:
#   "model": "anthropic/claude-opus-4.8"
```

## FAQ

### Is OpenAI o3 cheaper than Claude Opus 4.8?

At current posted rates, Claude Opus 4.8 is the cheaper of the two (input $3.00 vs $2.25, output $12.00 vs $11.25 per 1M tokens). Rates change; the /models page is the live source of truth.

### Can I switch between OpenAI o3 and Claude Opus 4.8 without changing code?

Yes. Both are served through the same OpenAI-compatible endpoint, so switching is changing the model string in the request — the key, base URL, and request shape stay identical.

### Where do these numbers come from?

Specs and prices on this page render from the live Router One catalog — the same data as the /models page — and refresh with it. Pricing methodology is documented on /pricing-methodology. Rates on this page were read from the live catalog on 2026-08-26 (UTC) and refresh within the hour.

## More comparisons

- [Claude Opus 4.8 vs GPT-5.5](https://router.one/models/compare/claude-opus-4-8-vs-gpt-5-5)
- [Claude Opus 4.8 vs Claude Sonnet 5](https://router.one/models/compare/claude-opus-4-8-vs-claude-sonnet-5)
- [Claude Opus 5 vs Claude Opus 4.8](https://router.one/models/compare/claude-opus-5-vs-claude-opus-4-8)

## See also

- Canonical page: https://router.one/models/compare/o3-vs-claude-opus-4-8
- All model comparisons: https://router.one/models/compare
- All models & prices: https://router.one/models (markdown: https://router.one/models.md)
- Pricing: https://router.one/pricing
- GPT API access: https://router.one/cheap-gpt-api
- Claude API access: https://router.one/cheap-claude-api
- Cost calculator: https://router.one/llm-cost-calculator
- Pricing methodology: https://router.one/pricing-methodology