Model Comparison

o1 vs Grok-1.5Which is better in 2026?

o1 significantly outperforms across most benchmarks.

Verdict: o1 vs Grok-1.5 — which is better?

o1 (by OpenAI) and Grok-1.5 (by xAI) 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.

o1 outperforms in 7 benchmarks (GPQA, GSM8k, HumanEval, MATH, MathVista, MMLU, MMMU), while Grok-1.5 is better at 0 benchmarks. o1 significantly outperforms across most benchmarks.

Choose o1 if…

  • you want the strongest raw capability — it leads on 7 of 7 shared benchmarks
  • you want the most recent training data — it shipped Dec 2024

Choose Grok-1.5 if…

  • you are already invested in the xAI ecosystem

Performance Benchmarks

Comparative analysis across standard metrics

7 benchmarks

o1 outperforms in 7 benchmarks (GPQA, GSM8k, HumanEval, MATH, MathVista, MMLU, MMMU), while Grok-1.5 is better at 0 benchmarks.

o1 significantly outperforms across most benchmarks.

Sun Jul 05 2026 • llm-stats.com

Arena Performance

Human preference votes

Context Window

Maximum input and output token capacity

Only o1 specifies input context (200,000 tokens). Only o1 specifies output context (100,000 tokens).

OpenAI
o1
Input200,000 tokens
Output100,000 tokens
xAI
Grok-1.5
Input- tokens
Output- tokens
Sun Jul 05 2026 • llm-stats.com

License

Usage and distribution terms

Both models are licensed under proprietary licenses.

Both models have usage restrictions defined by their respective organizations.

o1

Proprietary

Closed source

Grok-1.5

Proprietary

Closed source

Release Timeline

When each model was launched

o1 was released on 2024-12-17, while Grok-1.5 was released on 2024-03-28.

o1 is 9 months newer than Grok-1.5.

o1

Dec 17, 2024

1.5 years ago

8mo newer
Grok-1.5

Mar 28, 2024

2.3 years ago

Knowledge Cutoff

When training data ends

Neither model specifies a knowledge cutoff date.

Unable to compare the recency of their training data.

No cutoff dates available

Outputs Comparison

Notice missing or incorrect data?Start an Issue discussion→

Key Takeaways

OpenAI
Larger context window (200,000 tokens)
Higher GPQA score (78.0% vs 35.9%)
Higher GSM8k score (97.1% vs 90.0%)
Higher HumanEval score (88.1% vs 74.1%)
Higher MATH score (96.4% vs 50.6%)
Higher MathVista score (71.8% vs 52.8%)
Higher MMLU score (91.8% vs 81.3%)
Higher MMMU score (77.6% vs 53.6%)
xAI

No standout differentiators in the data we have for this pair.

Detailed Comparison

Interactive Arena

Judge for yourself.

Run your own prompts against o1 and Grok-1.5 side-by-side, then vote on the output you prefer.

o1
✓ Preferred
Grok-1.5
Open in Playground
AI Model Comparison Table
Feature
OpenAI
o1
xAI
Grok-1.5

FAQ

Common questions about o1 vs Grok-1.5.

Which is better, o1 or Grok-1.5?

o1 significantly outperforms across most benchmarks. o1 is made by OpenAI and Grok-1.5 is made by xAI. The best choice depends on your use case — compare their benchmark scores, pricing, and capabilities above.

How does o1 compare to Grok-1.5 in benchmarks?

o1 scores GSM8k: 97.1%, MATH: 96.4%, GPQA Physics: 92.8%, MMLU: 91.8%, MGSM: 89.3%. Grok-1.5 scores GSM8k: 90.0%, DocVQA: 85.6%, MMLU: 81.3%, HumanEval: 74.1%, MMMU: 53.6%.

What are the context window sizes for o1 and Grok-1.5?

o1 supports 200K tokens and Grok-1.5 supports an unknown number of tokens. A larger context window lets you process longer documents, conversations, or codebases in a single request.

Who makes o1 and Grok-1.5?

o1 is developed by OpenAI and Grok-1.5 is developed by xAI.

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