GPT-5.5 vs gpt-oss-20b
How do these models stack up? Below is an expert side-by-side comparison of specifications, context window capacity, live pricing per million tokens, and standardized benchmark scores for GPT-5.5 and gpt-oss-20b.
GPT-5.5
GPT-5.5 is OpenAI’s frontier model designed for complex professional workloads, building on GPT-5.4 with stronger reasoning, higher reliability, and improved token efficiency on hard tasks. It features a 1M+ token...
gpt-oss-20b
gpt-oss-20b is an open-weight 21B parameter model released by OpenAI under the Apache 2.0 license. It uses a Mixture-of-Experts (MoE) architecture with 3.6B active parameters per forward pass, optimized for...
Technical Specifications
| Specification | GPT-5.5 | gpt-oss-20b |
|---|---|---|
| Provider | OpenAI | OpenAI |
| Context Window | 1,050,000 tokens | 131,072 tokens |
| Agent Suitability | 95/100 | N/A |
| Time to First Token (TTFT) | 380 ms | N/A |
| Deployment Model | managed api | managed api |
| Production Stability | stable | stable |
| API Available | Yes | Yes |
| Released Date | 2026-04-24 | 2025-08-05 |
API Pricing Comparison
Input Price per Million Tokens
GPT-5.5
$5.00
gpt-oss-20b
$0.03
Output Price per Million Tokens
GPT-5.5
$30.00
gpt-oss-20b
$0.14
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Benchmark Performance Metrics
Scores show the raw performance percentages verified across key evaluation suites. Higher bars indicate superior accuracy and capability in that domain.
GPT-5.5 Quirks & Gotchas
- ▸Best for JSON schema adherence — strict mode available via response_format parameter
- ▸Requires explicit tool_choice for deterministic function calling
gpt-oss-20b Quirks & Gotchas
No developer gotchas reported.