AI model comparison
GPT-6 Luna vs gpt-oss-20b
Side by side comparison of GPT-6 Luna and gpt-oss-20b on pricing, benchmark scores, context window, and more.
GPT-6 Luna is the fast, cost-efficient model in OpenAI's GPT-6 series, positioned below GPT-6 Sol.
- Input / 1M
- $0.10
- Output / 1M
- $0.50
- Context
- 1.05M
gpt-oss-20b is an open-weight 21B parameter model released by OpenAI under the Apache 2.0 license.
- Input / 1M
- $0.02
- Output / 1M
- $0.09
- Context
- 131K
Comparing image generators? Compare image models
At a glance
Quick verdict
How the two models stack up on the things people ask about most.
Lower price
gpt-oss-20b
5.6x cheaper for a typical chat
Higher intelligence score
Not available
Not enough benchmark data
Larger context window
GPT-6 Luna
1.05M vs 131K tokens
Newer release
GPT-6 Luna
Released September 22, 2026
Benchmarks
Benchmark scores
Independent scores from Artificial Analysis. Higher is better.
Intelligence index
GPT-6 Luna27.8gpt-oss-20bNot availableCoding index
GPT-6 LunaNot availablegpt-oss-20b20.7Agentic index
GPT-6 LunaNot availablegpt-oss-20b1.2Pricing
GPT-6 Luna vs gpt-oss-20b API pricing
Per-token API rates. Cheaper option highlighted.
| Metric | GPT-6 Luna | gpt-oss-20b |
|---|---|---|
| Input tokensPer 1M tokens | $0.10 | $0.02 |
| Output tokensPer 1M tokens | $0.50 | $0.09 |
| Cached input (read)Per 1M tokens | $0.01 | $0.01 |
| Cache writePer 1M tokens | $0.13 | Not available |
| Long-context pricingPer 1M tokens, for very long prompts | $0.20 in / $0.75 out above 272K | Same rate at any length |
| Web searchPer request | $0.01 | Not available |
What it costs in practice
Estimated cost per 1,000 requests at standard rates. Coding and long-document figures also show the cost when the input is already cached.
Chat message
2K in, 500 out
GPT-6 Luna$0.45gpt-oss-20b$0.08Coding task
30K in, 4K out
GPT-6 Luna$5$2.30 cachedgpt-oss-20b$0.90$0.63 cachedLong document summary
150K in, 2K out
GPT-6 Luna$16$2.50 cachedgpt-oss-20b$2.88$1.53 cachedSpecs
Context window and capabilities
How much each model can read, how much it can write, and what it accepts as input.
| Metric | GPT-6 Luna | gpt-oss-20b |
|---|---|---|
| Context window | 1.05M tokens | 131K tokens |
| Max output | 128K tokens | 33K tokens |
| Input types | File, Image, Text | Text |
| Output types | Text | Text |
| Reasoning effort levels | Max, Extra high, High, Medium, Low, None | High, Medium, Low |
| Default reasoning effort | Medium | Medium |
| Release date | September 22, 2026 | August 5, 2025 |
Features
Supported features
API features available for each model.
| Metric | GPT-6 Luna | gpt-oss-20b |
|---|---|---|
| Tool calling | Supported | Supported |
| Structured outputs | Supported | Supported |
| JSON mode | Supported | Supported |
| Reasoning | Supported | Supported |
| Temperature | Not supported | Supported |
| Stop sequences | Not supported | Supported |
| Deterministic seed | Supported | Supported |
| Verbosity control | Supported | Not supported |
Keep exploring
More on these models
Other head-to-heads, the full model page, and the alternatives list for each model.
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gpt-oss-20bView full model details- gpt-oss-20b vs DeepSeek V4.1 Flash 1017
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Our take
gpt-oss-20b is 5.6x cheaper for a typical chat. GPT-6 Luna has the larger context window (1.05M vs 131K tokens). The right pick depends on your workload, so the quickest way to settle it is to send the same prompt to both and compare.
FAQ
Frequently asked questions
Is GPT-6 Luna or gpt-oss-20b cheaper?
gpt-oss-20b is cheaper for a typical chat (2K input tokens and 500 output tokens). gpt-oss-20b costs $0.02 per 1M input tokens and $0.09 per 1M output tokens, while GPT-6 Luna costs $0.10 per 1M input tokens and $0.50 per 1M output tokens.
Which has a bigger context window, GPT-6 Luna or gpt-oss-20b?
GPT-6 Luna supports up to 1.05M tokens of context, compared with 131K for gpt-oss-20b.
Can I use GPT-6 Luna and gpt-oss-20b at the same time?
Yes. Shortcut Chat sends one prompt to multiple models at once, so you can see GPT-6 Luna and gpt-oss-20b answer side by side and keep the better response.
Why choose? Ask both.
Send one prompt to GPT-6 Luna and gpt-oss-20b at the same time. Compare the answers side by side and keep the best one.