Model Comparison

GPT-5 Codex vs Phi 4Which is better in 2026?

Comparing GPT-5 Codex and Phi 4 across benchmarks, pricing, and capabilities.

Verdict: GPT-5 Codex vs Phi 4 — which is better?

GPT-5 Codex (by OpenAI) and Phi 4 (by Microsoft) 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.

Choose GPT-5 Codex if…

  • you want the most recent training data — it shipped Sep 2025

Choose Phi 4 if…

  • you need open weights you can self-host or fine-tune

Performance Benchmarks

Comparative analysis across standard metrics

No common benchmarks found

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

Arena Performance

Human preference votes

Context Window

Maximum input and output token capacity

Only Phi 4 specifies input context (16,000 tokens). Only Phi 4 specifies output context (16,000 tokens).

OpenAI
GPT-5 Codex
Input- tokens
Output- tokens
Microsoft
Phi 4
Input16,000 tokens
Output16,000 tokens
Sat Jun 27 2026 • llm-stats.com

License

Usage and distribution terms

GPT-5 Codex is licensed under a proprietary license, while Phi 4 uses MIT.

License differences may affect how you can use these models in commercial or open-source projects.

GPT-5 Codex

Proprietary

Closed source

Phi 4

MIT

Open weights

Release Timeline

When each model was launched

GPT-5 Codex was released on 2025-09-15, while Phi 4 was released on 2024-12-12.

GPT-5 Codex is 9 months newer than Phi 4.

GPT-5 Codex

Sep 15, 2025

9 months ago

9mo newer
Phi 4

Dec 12, 2024

1.5 years ago

Knowledge Cutoff

When training data ends

GPT-5 Codex has a knowledge cutoff of 2024-09-30, while Phi 4 has a cutoff of 2024-06-01.

GPT-5 Codex has more recent training data (up to 2024-09-30), making it potentially better informed about events through that date compared to Phi 4 (2024-06-01).

GPT-5 Codex

Sep 2024

3 mo newer
Phi 4

Jun 2024

Outputs Comparison

Notice missing or incorrect data?Start an Issue discussion→

Key Takeaways

OpenAI

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

Microsoft
Larger context window (16,000 tokens)
Has open weights

Detailed Comparison

Interactive Arena

Judge for yourself.

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

GPT-5 Codex
✓ Preferred
Phi 4
Open in Playground
AI Model Comparison Table
Feature
OpenAI
GPT-5 Codex
Microsoft
Phi 4

FAQ

Common questions about GPT-5 Codex vs Phi 4.

Which is better, GPT-5 Codex or Phi 4?

GPT-5 Codex (OpenAI) and Phi 4 (Microsoft) 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 Codex compare to Phi 4 in benchmarks?

GPT-5 Codex scores SWE-Bench Verified: 74.5%. Phi 4 scores MMLU: 84.8%, HumanEval+: 82.8%, HumanEval: 82.6%, MGSM: 80.6%, MATH: 80.4%.

What are the context window sizes for GPT-5 Codex and Phi 4?

GPT-5 Codex supports an unknown number of tokens and Phi 4 supports 16K 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 Codex and Phi 4?

Key differences include licensing (Proprietary vs MIT). See the full comparison above for benchmark-by-benchmark results.

Who makes GPT-5 Codex and Phi 4?

GPT-5 Codex is developed by OpenAI and Phi 4 is developed by Microsoft.

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