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GPT-5 Codex vs Grok-4 Heavy

GPT-5 Codex and Grok-4 Heavy are closely matched at 26.8 and 40.9 on the LLM Stats Score.

OpenAI · xAI · Updated for 2026

Which is better?

GPT-5 Codex and Grok-4 Heavy are closely matched on the overall LLM Stats Score at 26.8 and 40.9.

Based on current LLM Stats indexes, shared benchmarks, pricing, and model metadata for 2026.

Choose GPT-5 Codex

  • you are already invested in the OpenAI ecosystem

Choose Grok-4 Heavy

  • you are already invested in the xAI ecosystem

At a glance

The differences that matter most.

GPT-5 Codex
OpenAI
Grok-4 Heavy
xAI
Core performance indexes
LLM Stats Score
26.8
#138
40.9
#50
Reasoning
26.7
#137
39.2
#53
Coding
19.4
#99
17.9
#108
Cost, coverage & limits
Benchmark wins
—
—
Input price
— / M
— / M
Output price
— / M
— / M
Context window
—
—

Individual benchmarks

1 reported for GPT-5 Codex · 6 for Grok-4 Heavy

No common benchmarks found

GPT-5 Codex and Grok-4 Heavydon't have any common benchmark datasets to compare. They may have been evaluated on different testing suites.

Human preference

Blind head-to-head votes and playground preference scores

Input capabilities

Documented input modalities across available providers

Grok-4 Heavy supports multimodal inputs, whereas GPT-5 Codex does not.

Grok-4 Heavy can handle both text and other forms of data like images, making it suitable for multimodal applications.

GPT-5 Codex

Text
Images
Audio
Video

Grok-4 Heavy

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 Codex

Proprietary

Closed source

Grok-4 Heavy

Proprietary

Closed source

Release Timeline

When each model was launched

GPT-5 Codex was released on 2025-09-15, while Grok-4 Heavy's release date is not specified.

We can confirm GPT-5 Codex's release timeline, but cannot make a direct age comparison without Grok-4 Heavy's release date.

GPT-5 Codex

Sep 15, 2025

11 months ago

Grok-4 Heavy

—

Knowledge Cutoff

When training data ends

GPT-5 Codex has a knowledge cutoff of 2024-09-30, while Grok-4 Heavy has a cutoff of 2024-12-31.

Grok-4 Heavy has more recent training data (up to 2024-12-31), making it potentially better informed about events through that date compared to GPT-5 Codex (2024-09-30).

GPT-5 Codex

Sep 2024

Grok-4 Heavy

Dec 2024

3 mo newer

Outputs Comparison

Notice missing or incorrect data?Start an Issue discussion→

Judge for yourself.

Run your own prompts against GPT-5 Codex and Grok-4 Heavy side-by-side, then vote on the output you prefer.

GPT-5 Codex
✓ Preferred
Grok-4 Heavy
Open in Playground

FAQ

Common questions about GPT-5 Codex vs Grok-4 Heavy.

Which is better, GPT-5 Codex or Grok-4 Heavy?

GPT-5 Codex and Grok-4 Heavy are closely matched on the LLM Stats Score at 26.8 and 40.9. GPT-5 Codex is made by OpenAI and Grok-4 Heavy is made by xAI. The best choice depends on your use case — compare their capability indexes, individual benchmarks, pricing, and limits above.

How does GPT-5 Codex compare to Grok-4 Heavy in benchmarks?

GPT-5 Codex scores SWE-Bench Verified: 74.5%. Grok-4 Heavy scores AIME 2025: 100.0%, HMMT25: 96.7%, GPQA: 88.4%, LiveCodeBench: 79.4%, USAMO25: 61.9%.

What are the main differences between GPT-5 Codex and Grok-4 Heavy?

Key differences include LLM Stats Score (26.8 vs 40.9), multimodal support (no vs yes). See the full comparison above for benchmark-by-benchmark results.

Who makes GPT-5 Codex and Grok-4 Heavy?

GPT-5 Codex is developed by OpenAI and Grok-4 Heavy is developed by xAI.

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