Model Comparison

Claude Opus 5 vs GPT-5.1 CodexWhich is better in 2026?

Comparing Claude Opus 5 and GPT-5.1 Codex across benchmarks, pricing, and capabilities.

Verdict: Claude Opus 5 vs GPT-5.1 Codex — which is better?

Claude Opus 5 (by Anthropic) and GPT-5.1 Codex (by OpenAI) are two of the AI models people compare most. Here is how they stack up on benchmarks, price and capabilities, and which one to pick in 2026.

On price, GPT-5.1 Codex is roughly 2.9x cheaper per token on a blended 3:1 input/output basis, which adds up quickly at production volume.

Claude Opus 5 also accepts a larger context window (1,000,000 input tokens), making it the stronger choice for long documents and large codebases.

Choose Claude Opus 5 if…

  • you process long inputs — it offers a 1,000,000 token context window
  • you want the most recent training data — it shipped Jul 2026

Choose GPT-5.1 Codex if…

  • cost matters — it's about 2.9x cheaper per token

Performance Benchmarks

Comparative analysis across standard metrics

No common benchmarks found

Claude Opus 5 and GPT-5.1 Codexdon't have any common benchmark datasets to compare. They may have been evaluated on different testing suites.

Arena Performance

Human preference votes

Pricing Analysis

Price comparison per million tokens

GPT-5.1 Codex costs less

For input processing, Claude Opus 5 ($5.00/1M tokens) is 4.0x more expensive than GPT-5.1 Codex ($1.25/1M tokens).

For output processing, Claude Opus 5 ($25.00/1M tokens) is 2.5x more expensive than GPT-5.1 Codex ($10.00/1M tokens).

In conclusion, Claude Opus 5 is more expensive than GPT-5.1 Codex.*

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

Lowest available price from all providers
Sat Jul 25 2026 • llm-stats.com
Anthropic
Claude Opus 5
Input tokens$5.00
Output tokens$25.00
Best providerAnthropic
OpenAI
GPT-5.1 Codex
Input tokens$1.25
Output tokens$10.00
Best providerOpenAI
Notice missing or incorrect data?Start an Issue→

Context Window

Maximum input and output token capacity

Claude Opus 5 accepts 1,000,000 input tokens compared to GPT-5.1 Codex's 400,000 tokens. Both models can generate responses up to 128,000 tokens.

Anthropic
Claude Opus 5
Input1,000,000 tokens
Output128,000 tokens
OpenAI
GPT-5.1 Codex
Input400,000 tokens
Output128,000 tokens
Sat Jul 25 2026 • llm-stats.com

Input Capabilities

Supported data types and modalities

Both Claude Opus 5 and GPT-5.1 Codex support multimodal inputs.

They are both capable of processing various types of data, offering versatility in application.

Claude Opus 5

Text
Images
Audio
Video

GPT-5.1 Codex

Text
Images
Audio
Video

License

Usage and distribution terms

Both models are licensed under proprietary licenses.

Both models have usage restrictions defined by their respective organizations.

Claude Opus 5

Proprietary

Closed source

GPT-5.1 Codex

Proprietary

Closed source

Release Timeline

When each model was launched

Claude Opus 5 was released on 2026-07-24, while GPT-5.1 Codex was released on 2025-11-19.

Claude Opus 5 is 8 months newer than GPT-5.1 Codex.

Claude Opus 5

Jul 24, 2026

1 days ago

8mo newer
GPT-5.1 Codex

Nov 19, 2025

8 months ago

Knowledge Cutoff

When training data ends

GPT-5.1 Codex has a documented knowledge cutoff of 2024-09-30, while Claude Opus 5's cutoff date is not specified.

We can confirm GPT-5.1 Codex's training data extends to 2024-09-30, but cannot make a direct comparison without Claude Opus 5's cutoff date.

Claude Opus 5

—

GPT-5.1 Codex

Sep 2024

Provider Availability

Claude Opus 5 is available from Anthropic. GPT-5.1 Codex is available from OpenAI.

Claude Opus 5

anthropic logo
Anthropic
Input Price:Input: $5.00/1MOutput Price:Output: $25.00/1M

GPT-5.1 Codex

openai logo
OpenAI
Input Price:Input: $1.25/1MOutput Price:Output: $10.00/1M
* Prices shown are per million tokens

Outputs Comparison

Notice missing or incorrect data?Start an Issue discussion→

Key Takeaways

Anthropic
Larger context window (1,000,000 tokens)
OpenAI
Less expensive input tokens
Less expensive output tokens

Detailed Comparison

Interactive Arena

Judge for yourself.

Run your own prompts against Claude Opus 5 and GPT-5.1 Codex side-by-side, then vote on the output you prefer.

Claude Opus 5
✓ Preferred
GPT-5.1 Codex
Open in Playground
AI Model Comparison Table
Feature
Anthropic
Claude Opus 5
OpenAI
GPT-5.1 Codex

FAQ

Common questions about Claude Opus 5 vs GPT-5.1 Codex.

Which is better, Claude Opus 5 or GPT-5.1 Codex?

Claude Opus 5 (Anthropic) and GPT-5.1 Codex (OpenAI) each have strengths in different areas. Compare their benchmark scores, pricing, context windows, and capabilities above to determine which fits your needs.

How does Claude Opus 5 compare to GPT-5.1 Codex in benchmarks?

Claude Opus 5 scores BrowseComp: 90.8%, BioMysteryBench: 90.1%, OSWorld 2.0: 70.6%, DeepSWE 1.1: 68.8%, Humanity's Last Exam: 64.7%. GPT-5.1 Codex scores SWE-Bench Verified: 73.7%, SWE-Lancer: 66.3%, Terminal-Bench 2.0: 52.8%.

Is Claude Opus 5 cheaper than GPT-5.1 Codex?

GPT-5.1 Codex is 4.0x cheaper for input tokens. Claude Opus 5 costs $5.00/M input and $25.00/M output via anthropic. GPT-5.1 Codex costs $1.25/M input and $10.00/M output via openai.

What are the context window sizes for Claude Opus 5 and GPT-5.1 Codex?

Claude Opus 5 supports 1.0M tokens and GPT-5.1 Codex supports 400K tokens. A larger context window lets you process longer documents, conversations, or codebases in a single request.

What are the main differences between Claude Opus 5 and GPT-5.1 Codex?

Key differences include context window (1.0M vs 400K), input pricing ($5.00 vs $1.25/M). See the full comparison above for benchmark-by-benchmark results.

Who makes Claude Opus 5 and GPT-5.1 Codex?

Claude Opus 5 is developed by Anthropic and GPT-5.1 Codex is developed by OpenAI.

Related comparisons