Model Comparison

GPT-5.1 Codex vs Grok 4.5Which is better in 2026?

Comparing GPT-5.1 Codex and Grok 4.5 across benchmarks, pricing, and capabilities.

Verdict: GPT-5.1 Codex vs Grok 4.5 — which is better?

GPT-5.1 Codex (by OpenAI) and Grok 4.5 (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.

On price, Grok 4.5 is roughly 1.1x cheaper per token on a blended 3:1 input/output basis, which adds up quickly at production volume.

Grok 4.5 also accepts a larger context window (500,000 input tokens), making it the stronger choice for long documents and large codebases.

Choose GPT-5.1 Codex if…

  • you want predictable pricing at $1.25/M input and $10.00/M output

Choose Grok 4.5 if…

  • cost matters — it's about 1.1x cheaper per token
  • you process long inputs — it offers a 500,000 token context window
  • you want the most recent training data — it shipped Jul 2026

Performance Benchmarks

Comparative analysis across standard metrics

No common benchmarks found

GPT-5.1 Codex and Grok 4.5don'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

Grok 4.5 costs less

For input processing, GPT-5.1 Codex ($1.25/1M tokens) is 1.6x cheaper than Grok 4.5 ($2.00/1M tokens).

For output processing, GPT-5.1 Codex ($10.00/1M tokens) is 1.7x more expensive than Grok 4.5 ($6.00/1M tokens).

In conclusion, GPT-5.1 Codex is more expensive than Grok 4.5.*

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

Lowest available price from all providers
Sat Jul 25 2026 • llm-stats.com
OpenAI
GPT-5.1 Codex
Input tokens$1.25
Output tokens$10.00
Best providerOpenAI
xAI
Grok 4.5
Input tokens$2.00
Output tokens$6.00
Best providerxAI
Notice missing or incorrect data?Start an Issue→

Context Window

Maximum input and output token capacity

Grok 4.5 accepts 500,000 input tokens compared to GPT-5.1 Codex's 400,000 tokens. Only GPT-5.1 Codex specifies output context (128,000 tokens).

OpenAI
GPT-5.1 Codex
Input400,000 tokens
Output128,000 tokens
xAI
Grok 4.5
Input500,000 tokens
Output- tokens
Sat Jul 25 2026 • llm-stats.com

Input Capabilities

Supported data types and modalities

Both GPT-5.1 Codex and Grok 4.5 support multimodal inputs.

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

GPT-5.1 Codex

Text
Images
Audio
Video

Grok 4.5

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.

GPT-5.1 Codex

Proprietary

Closed source

Grok 4.5

Proprietary

Closed source

Release Timeline

When each model was launched

GPT-5.1 Codex was released on 2025-11-19, while Grok 4.5 was released on 2026-07-16.

Grok 4.5 is 8 months newer than GPT-5.1 Codex.

GPT-5.1 Codex

Nov 19, 2025

8 months ago

Grok 4.5

Jul 16, 2026

1 weeks ago

7mo newer

Knowledge Cutoff

When training data ends

GPT-5.1 Codex has a knowledge cutoff of 2024-09-30, while Grok 4.5 has a cutoff of 2026-02-01.

Grok 4.5 has more recent training data (up to 2026-02-01), making it potentially better informed about events through that date compared to GPT-5.1 Codex (2024-09-30).

GPT-5.1 Codex

Sep 2024

Grok 4.5

Feb 2026

1.4 yr newer

Provider Availability

GPT-5.1 Codex is available from OpenAI. Grok 4.5 is available from xAI.

GPT-5.1 Codex

openai logo
OpenAI
Input Price:Input: $1.25/1MOutput Price:Output: $10.00/1M

Grok 4.5

xai logo
xAI
Input Price:Input: $2.00/1MOutput Price:Output: $6.00/1M
* Prices shown are per million tokens

Outputs Comparison

Notice missing or incorrect data?Start an Issue discussion→

Key Takeaways

OpenAI
Less expensive input tokens
xAI
Larger context window (500,000 tokens)
Less expensive output tokens

Detailed Comparison

Interactive Arena

Judge for yourself.

Run your own prompts against GPT-5.1 Codex and Grok 4.5 side-by-side, then vote on the output you prefer.

GPT-5.1 Codex
✓ Preferred
Grok 4.5
Open in Playground
AI Model Comparison Table
Feature
OpenAI
GPT-5.1 Codex
xAI
Grok 4.5

FAQ

Common questions about GPT-5.1 Codex vs Grok 4.5.

Which is better, GPT-5.1 Codex or Grok 4.5?

GPT-5.1 Codex (OpenAI) and Grok 4.5 (xAI) each have strengths in different areas. Compare their benchmark scores, pricing, context windows, and capabilities above to determine which fits your needs.

How does GPT-5.1 Codex compare to Grok 4.5 in benchmarks?

GPT-5.1 Codex scores SWE-Bench Verified: 73.7%, SWE-Lancer: 66.3%, Terminal-Bench 2.0: 52.8%. Grok 4.5 scores GPQA: 93.0%, Terminal-Bench 2.1: 83.3%, Artificial Analysis Coding Agent Index v1.1: 76.0%, SWE-Bench Pro: 64.7%, AA-Omniscience Index: 63.0%.

Is GPT-5.1 Codex cheaper than Grok 4.5?

GPT-5.1 Codex is 1.6x cheaper for input tokens. GPT-5.1 Codex costs $1.25/M input and $10.00/M output via openai. Grok 4.5 costs $2.00/M input and $6.00/M output via xai.

What are the context window sizes for GPT-5.1 Codex and Grok 4.5?

GPT-5.1 Codex supports 400K tokens and Grok 4.5 supports 500K tokens. A larger context window lets you process longer documents, conversations, or codebases in a single request.

What are the main differences between GPT-5.1 Codex and Grok 4.5?

Key differences include context window (400K vs 500K), input pricing ($1.25 vs $2.00/M). See the full comparison above for benchmark-by-benchmark results.

Who makes GPT-5.1 Codex and Grok 4.5?

GPT-5.1 Codex is developed by OpenAI and Grok 4.5 is developed by xAI.

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