GPT-4o 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-4o and gpt-oss-20b.
GPT-4o
GPT-4o ("o" for "omni") is OpenAI's latest AI model, supporting both text and image inputs with text outputs. It maintains the intelligence level of [GPT-4 Turbo](/models/openai/gpt-4-turbo) while being twice as...
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-4o | gpt-oss-20b |
|---|---|---|
| Provider | OpenAI | OpenAI |
| Context Window | 128,000 tokens | 131,072 tokens |
| Agent Suitability | 90/100 | N/A |
| Time to First Token (TTFT) | 280 ms | N/A |
| Deployment Model | managed api | managed api |
| Production Stability | stable | stable |
| API Available | Yes | Yes |
| Released Date | 2024-05-13 | 2025-08-05 |
API Pricing Comparison
Input Price per Million Tokens
GPT-4o
$2.50
gpt-oss-20b
$0.03
Output Price per Million Tokens
GPT-4o
$10.00
gpt-oss-20b
$0.14
Want to test both models live?
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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-4o Quirks & Gotchas
- ▸Strong multimodal performance — best vision+tool calling combo
- ▸Legacy model — migrate to GPT-5 for latest improvements
gpt-oss-20b Quirks & Gotchas
No developer gotchas reported.