Model Comparison

GPT-4.5 vs GPT-5 CodexWhich is better in 2026?

GPT-5 Codex significantly outperforms across most benchmarks.

Verdict: GPT-4.5 vs GPT-5 Codex — which is better?

GPT-4.5 (by OpenAI) and GPT-5 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.

GPT-4.5 outperforms in 0 benchmarks, while GPT-5 Codex is better at 1 benchmark (SWE-Bench Verified). GPT-5 Codex significantly outperforms across most benchmarks.

Choose GPT-4.5 if…

  • you want predictable pricing at $75.00/M input and $150.00/M output

Choose GPT-5 Codex if…

  • you want the strongest raw capability — it leads on 1 of 1 shared benchmarks
  • you want the most recent training data — it shipped Sep 2025

Performance Benchmarks

Comparative analysis across standard metrics

1 benchmarks

GPT-4.5 outperforms in 0 benchmarks, while GPT-5 Codex is better at 1 benchmark (SWE-Bench Verified).

GPT-5 Codex significantly outperforms across most benchmarks.

Sun Jul 26 2026 • llm-stats.com

Arena Performance

Human preference votes

Context Window

Maximum input and output token capacity

Only GPT-4.5 specifies input context (128,000 tokens). Only GPT-4.5 specifies output context (4,096 tokens).

OpenAI
GPT-4.5
Input128,000 tokens
Output4,096 tokens
OpenAI
GPT-5 Codex
Input- tokens
Output- tokens
Sun Jul 26 2026 • llm-stats.com

Input Capabilities

Supported data types and modalities

GPT-4.5 supports multimodal inputs, whereas GPT-5 Codex does not.

GPT-4.5 can handle both text and other forms of data like images, making it suitable for multimodal applications.

GPT-4.5

Text
Images
Audio
Video

GPT-5 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.

GPT-4.5

Proprietary

Closed source

GPT-5 Codex

Proprietary

Closed source

Release Timeline

When each model was launched

GPT-4.5 was released on 2025-02-27, while GPT-5 Codex was released on 2025-09-15.

GPT-5 Codex is 7 months newer than GPT-4.5.

GPT-4.5

Feb 27, 2025

1.4 years ago

GPT-5 Codex

Sep 15, 2025

10 months ago

6mo newer

Knowledge Cutoff

When training data ends

GPT-5 Codex has a documented knowledge cutoff of 2024-09-30, while GPT-4.5's cutoff date is not specified.

We can confirm GPT-5 Codex's training data extends to 2024-09-30, but cannot make a direct comparison without GPT-4.5's cutoff date.

GPT-4.5

—

GPT-5 Codex

Sep 2024

Outputs Comparison

Notice missing or incorrect data?Start an Issue discussion→

Key Takeaways

OpenAI
Larger context window (128,000 tokens)
Supports multimodal inputs
OpenAI
Higher SWE-Bench Verified score (74.5% vs 38.0%)

Detailed Comparison

Interactive Arena

Judge for yourself.

Run your own prompts against GPT-4.5 and GPT-5 Codex side-by-side, then vote on the output you prefer.

GPT-4.5
✓ Preferred
GPT-5 Codex
Open in Playground
AI Model Comparison Table
Feature
OpenAI
GPT-4.5
OpenAI
GPT-5 Codex

FAQ

Common questions about GPT-4.5 vs GPT-5 Codex.

Which is better, GPT-4.5 or GPT-5 Codex?

GPT-5 Codex significantly outperforms across most benchmarks. GPT-4.5 is made by OpenAI and GPT-5 Codex is made by OpenAI. The best choice depends on your use case — compare their benchmark scores, pricing, and capabilities above.

How does GPT-4.5 compare to GPT-5 Codex in benchmarks?

GPT-4.5 scores GSM8k: 97.0%, MMLU: 90.8%, CharXiv-D: 90.0%, IFEval: 88.2%, HumanEval: 88.0%. GPT-5 Codex scores SWE-Bench Verified: 74.5%.

What are the context window sizes for GPT-4.5 and GPT-5 Codex?

GPT-4.5 supports 128K tokens and GPT-5 Codex supports an unknown number of tokens. A larger context window lets you process longer documents, conversations, or codebases in a single request.

What are the main differences between GPT-4.5 and GPT-5 Codex?

Key differences include multimodal support (yes vs no). See the full comparison above for benchmark-by-benchmark results.

Related comparisons