Model Comparison

GPT-5.6 Luna vs GPT-5.5Which is better in 2026?

GPT-5.5 has a slight edge in benchmark performance. GPT-5.6 Luna is 5.0x cheaper per token.

Verdict: GPT-5.6 Luna vs GPT-5.5 — which is better?

GPT-5.6 Luna (by OpenAI) and GPT-5.5 (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-5.6 Luna outperforms in 4 benchmarks (FrontierMath, GDPval-AA, Graphwalks BFS >128k, SWE-Bench Pro), while GPT-5.5 is better at 5 benchmarks (BrowseComp, GPQA, MMMU-Pro, MRCR v2 (8-needle), Toolathlon). GPT-5.5 has a slight edge in benchmark performance.

On price, GPT-5.6 Luna is roughly 5.0x cheaper per token on a blended 3:1 input/output basis, which adds up quickly at production volume.

Choose GPT-5.6 Luna if…

  • cost matters — it's about 5.0x cheaper per token
  • you want the most recent training data — it shipped Jul 2026

Choose GPT-5.5 if…

  • you want the strongest raw capability — it leads on 5 of 9 shared benchmarks

Performance Benchmarks

Comparative analysis across standard metrics

9 benchmarks

GPT-5.6 Luna outperforms in 4 benchmarks (FrontierMath, GDPval-AA, Graphwalks BFS >128k, SWE-Bench Pro), while GPT-5.5 is better at 5 benchmarks (BrowseComp, GPQA, MMMU-Pro, MRCR v2 (8-needle), Toolathlon).

GPT-5.5 has a slight edge in benchmark performance.

Fri Jul 17 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-5.6 Luna ($1.00/1M tokens) is 5.0x cheaper than GPT-5.5 ($5.00/1M tokens).

For output processing, GPT-5.6 Luna ($6.00/1M tokens) is 5.0x cheaper than GPT-5.5 ($30.00/1M tokens).

In conclusion, GPT-5.5 is more expensive than GPT-5.6 Luna.*

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

Lowest available price from all providers
Fri Jul 17 2026 • llm-stats.com
OpenAI
GPT-5.6 Luna
Input tokens$1.00
Output tokens$6.00
Best providerOpenAI
OpenAI
GPT-5.5
Input tokens$5.00
Output tokens$30.00
Best providerOpenAI
Notice missing or incorrect data?Start an Issue→

Context Window

Maximum input and output token capacity

Both models have the same input context window of 1,050,000 tokens. Both models can generate responses up to 128,000 tokens.

OpenAI
GPT-5.6 Luna
Input1,050,000 tokens
Output128,000 tokens
OpenAI
GPT-5.5
Input1,050,000 tokens
Output128,000 tokens
Fri Jul 17 2026 • llm-stats.com

Input Capabilities

Supported data types and modalities

Both GPT-5.6 Luna and GPT-5.5 support multimodal inputs.

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

GPT-5.6 Luna

Text
Images
Audio
Video

GPT-5.5

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-5.6 Luna

Proprietary

Closed source

GPT-5.5

Proprietary

Closed source

Release Timeline

When each model was launched

GPT-5.6 Luna was released on 2026-07-09, while GPT-5.5 was released on 2026-04-23.

GPT-5.6 Luna is 3 months newer than GPT-5.5.

GPT-5.6 Luna

Jul 9, 2026

1 weeks ago

2mo newer
GPT-5.5

Apr 23, 2026

2 months ago

Knowledge Cutoff

When training data ends

GPT-5.6 Luna has a knowledge cutoff of 2026-02-16, while GPT-5.5 has a cutoff of 2025-12-01.

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-5.5 (2025-12-01).

GPT-5.6 Luna

Feb 2026

2 mo newer
GPT-5.5

Dec 2025

Provider Availability

GPT-5.6 Luna is available from OpenAI. GPT-5.5 is available from OpenAI.

GPT-5.6 Luna

openai logo
OpenAI
Input Price:Input: $1.00/1MOutput Price:Output: $6.00/1M

GPT-5.5

openai logo
OpenAI
Input Price:Input: $5.00/1MOutput Price:Output: $30.00/1M
* Prices shown are per million tokens

Outputs Comparison

Notice missing or incorrect data?Start an Issue discussion→

Key Takeaways

OpenAI
Less expensive input tokens
Less expensive output tokens
Higher FrontierMath score (78.6% vs 35.4%)
Higher GDPval-AA score (53.1% vs 37.8%)
Higher Graphwalks BFS >128k score (81.3% vs 45.4%)
Higher SWE-Bench Pro score (62.7% vs 58.6%)
OpenAI
Higher BrowseComp score (84.4% vs 83.3%)
Higher GPQA score (93.6% vs 92.3%)
Higher MMMU-Pro score (83.2% vs 78.4%)
Higher MRCR v2 (8-needle) score (74.0% vs 41.3%)
Higher Toolathlon score (55.6% vs 53.4%)

Detailed Comparison

Interactive Arena

Judge for yourself.

Run your own prompts against GPT-5.6 Luna and GPT-5.5 side-by-side, then vote on the output you prefer.

GPT-5.6 Luna
✓ Preferred
GPT-5.5
Open in Playground
AI Model Comparison Table
Feature
OpenAI
GPT-5.6 Luna
OpenAI
GPT-5.5

FAQ

Common questions about GPT-5.6 Luna vs GPT-5.5.

Which is better, GPT-5.6 Luna or GPT-5.5?

GPT-5.5 has a slight edge in benchmark performance. GPT-5.6 Luna is made by OpenAI and GPT-5.5 is made by OpenAI. The best choice depends on your use case — compare their benchmark scores, pricing, and capabilities above.

How does GPT-5.6 Luna compare to GPT-5.5 in benchmarks?

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%. GPT-5.5 scores Tau2 Telecom: 98.0%, ARC-AGI: 95.0%, GPQA: 93.6%, ARC-AGI v2: 85.0%, GDPval-MM: 84.9%.

Is GPT-5.6 Luna cheaper than GPT-5.5?

GPT-5.6 Luna is 5.0x cheaper for input tokens. GPT-5.6 Luna costs $1.00/M input and $6.00/M output via openai. GPT-5.5 costs $5.00/M input and $30.00/M output via openai.

What are the context window sizes for GPT-5.6 Luna and GPT-5.5?

GPT-5.6 Luna supports 1.1M tokens and GPT-5.5 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-5.6 Luna and GPT-5.5?

Key differences include input pricing ($1.00 vs $5.00/M). See the full comparison above for benchmark-by-benchmark results.

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