Model Comparison

GPT-5 Medium vs GPT-5.6 LunaWhich is better in 2026?

GPT-5.6 Luna significantly outperforms across most benchmarks. GPT-5.6 Luna is 1.5x cheaper per token.

Verdict: GPT-5 Medium vs GPT-5.6 Luna — which is better?

GPT-5 Medium (by OpenAI) and GPT-5.6 Luna (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-5 Medium outperforms in 0 benchmarks, while GPT-5.6 Luna is better at 1 benchmark (GPQA). GPT-5.6 Luna significantly outperforms across most benchmarks.

On price, GPT-5.6 Luna is roughly 1.5x cheaper per token on a blended 3:1 input/output basis, which adds up quickly at production volume.

GPT-5.6 Luna also accepts a larger context window (1,050,000 input tokens), making it the stronger choice for long documents and large codebases.

Choose GPT-5 Medium if…

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

Choose GPT-5.6 Luna if…

  • you want the strongest raw capability — it leads on 1 of 1 shared benchmarks
  • cost matters — it's about 1.5x cheaper per token
  • you process long inputs — it offers a 1,050,000 token context window
  • you want the most recent training data — it shipped Jul 2026

Performance Benchmarks

Comparative analysis across standard metrics

1 benchmarks

GPT-5 Medium outperforms in 0 benchmarks, while GPT-5.6 Luna is better at 1 benchmark (GPQA).

GPT-5.6 Luna significantly outperforms across most benchmarks.

Tue Jul 21 2026 • llm-stats.com

Arena Performance

Human preference votes

Pricing Analysis

Price comparison per million tokens

GPT-5.6 Luna costs less

For input processing, GPT-5 Medium ($1.25/1M tokens) is 1.3x more expensive than GPT-5.6 Luna ($1.00/1M tokens).

For output processing, GPT-5 Medium ($10.00/1M tokens) is 1.7x more expensive than GPT-5.6 Luna ($6.00/1M tokens).

In conclusion, GPT-5 Medium is more expensive than GPT-5.6 Luna.*

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

Lowest available price from all providers
Tue Jul 21 2026 • llm-stats.com
OpenAI
GPT-5 Medium
Input tokens$1.25
Output tokens$10.00
Best providerOpenAI
OpenAI
GPT-5.6 Luna
Input tokens$1.00
Output tokens$6.00
Best providerOpenAI
Notice missing or incorrect data?Start an Issue→

Context Window

Maximum input and output token capacity

GPT-5.6 Luna accepts 1,050,000 input tokens compared to GPT-5 Medium's 400,000 tokens. Both models can generate responses up to 128,000 tokens.

OpenAI
GPT-5 Medium
Input400,000 tokens
Output128,000 tokens
OpenAI
GPT-5.6 Luna
Input1,050,000 tokens
Output128,000 tokens
Tue Jul 21 2026 • llm-stats.com

Input Capabilities

Supported data types and modalities

Both GPT-5 Medium and GPT-5.6 Luna support multimodal inputs.

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

GPT-5 Medium

Text
Images
Audio
Video

GPT-5.6 Luna

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 Medium

Proprietary

Closed source

GPT-5.6 Luna

Proprietary

Closed source

Release Timeline

When each model was launched

GPT-5 Medium was released on 2025-08-07, while GPT-5.6 Luna was released on 2026-07-09.

GPT-5.6 Luna is 11 months newer than GPT-5 Medium.

GPT-5 Medium

Aug 7, 2025

11 months ago

GPT-5.6 Luna

Jul 9, 2026

1 weeks ago

11mo newer

Knowledge Cutoff

When training data ends

GPT-5 Medium has a knowledge cutoff of 2024-09-30, while GPT-5.6 Luna has a cutoff of 2026-02-16.

GPT-5.6 Luna has more recent training data (up to 2026-02-16), making it potentially better informed about events through that date compared to GPT-5 Medium (2024-09-30).

GPT-5 Medium

Sep 2024

GPT-5.6 Luna

Feb 2026

1.4 yr newer

Provider Availability

GPT-5 Medium is available from OpenAI. GPT-5.6 Luna is available from OpenAI.

GPT-5 Medium

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

GPT-5.6 Luna

openai logo
OpenAI
Input Price:Input: $1.00/1MOutput 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

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

OpenAI
Larger context window (1,050,000 tokens)
Less expensive input tokens
Less expensive output tokens
Higher GPQA score (92.3% vs 88.1%)

Detailed Comparison

Interactive Arena

Judge for yourself.

Run your own prompts against GPT-5 Medium and GPT-5.6 Luna side-by-side, then vote on the output you prefer.

GPT-5 Medium
✓ Preferred
GPT-5.6 Luna
Open in Playground
AI Model Comparison Table
Feature
OpenAI
GPT-5 Medium
OpenAI
GPT-5.6 Luna

FAQ

Common questions about GPT-5 Medium vs GPT-5.6 Luna.

Which is better, GPT-5 Medium or GPT-5.6 Luna?

GPT-5.6 Luna significantly outperforms across most benchmarks. GPT-5 Medium is made by OpenAI and GPT-5.6 Luna is made by OpenAI. The best choice depends on your use case — compare their benchmark scores, pricing, and capabilities above.

How does GPT-5 Medium compare to GPT-5.6 Luna in benchmarks?

GPT-5 Medium scores AIME 2025: 88.9%, GPQA: 88.1%. GPT-5.6 Luna scores Connectors: 99.9%, HealthBench Consensus: 95.1%, GPQA: 92.3%, Search and Function-Calling: 89.7%, Capture-the-Flag Challenges (Internal): 85.2%.

Is GPT-5 Medium cheaper than GPT-5.6 Luna?

GPT-5.6 Luna is 1.3x cheaper for input tokens. GPT-5 Medium costs $1.25/M input and $10.00/M output via openai. GPT-5.6 Luna costs $1.00/M input and $6.00/M output via openai.

What are the context window sizes for GPT-5 Medium and GPT-5.6 Luna?

GPT-5 Medium supports 400K tokens and GPT-5.6 Luna supports 1.1M 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 Medium and GPT-5.6 Luna?

Key differences include context window (400K vs 1.1M), input pricing ($1.25 vs $1.00/M). See the full comparison above for benchmark-by-benchmark results.

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