Model Comparison

GPT-5.3 Chat vs GPT OSS 20BWhich is better in 2026?

GPT-5.3 Chat significantly outperforms across most benchmarks. GPT OSS 20B is 55.0x cheaper per token.

Verdict: GPT-5.3 Chat vs GPT OSS 20B — which is better?

GPT-5.3 Chat (by OpenAI) and GPT OSS 20B (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-5.3 Chat outperforms in 2 benchmarks (HealthBench, HealthBench Hard), while GPT OSS 20B is better at 0 benchmarks. GPT-5.3 Chat significantly outperforms across most benchmarks.

On price, GPT OSS 20B is roughly 55.0x cheaper per token on a blended 3:1 input/output basis, which adds up quickly at production volume.

GPT OSS 20B also accepts a larger context window (131,072 input tokens), making it the stronger choice for long documents and large codebases.

Choose GPT-5.3 Chat if…

  • you want the strongest raw capability — it leads on 2 of 2 shared benchmarks
  • you want the most recent training data — it shipped Mar 2026

Choose GPT OSS 20B if…

  • cost matters — it's about 55.0x cheaper per token
  • you process long inputs — it offers a 131,072 token context window
  • you need open weights you can self-host or fine-tune

Performance Benchmarks

Comparative analysis across standard metrics

2 benchmarks

GPT-5.3 Chat outperforms in 2 benchmarks (HealthBench, HealthBench Hard), while GPT OSS 20B is better at 0 benchmarks.

GPT-5.3 Chat significantly outperforms across most benchmarks.

Sat Jul 25 2026 • llm-stats.com

Arena Performance

Human preference votes

Pricing Analysis

Price comparison per million tokens

GPT OSS 20B costs less

For input processing, GPT-5.3 Chat ($1.75/1M tokens) is 35.0x more expensive than GPT OSS 20B ($0.05/1M tokens).

For output processing, GPT-5.3 Chat ($14.00/1M tokens) is 70.0x more expensive than GPT OSS 20B ($0.20/1M tokens).

In conclusion, GPT-5.3 Chat is more expensive than GPT OSS 20B.*

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

Lowest available price from all providers
Sat Jul 25 2026 • llm-stats.com
OpenAI
GPT-5.3 Chat
Input tokens$1.75
Output tokens$14.00
Best providerOpenAI
OpenAI
GPT OSS 20B
Input tokens$0.05
Output tokens$0.20
Best providerNovita
Notice missing or incorrect data?Start an Issue→

Context Window

Maximum input and output token capacity

GPT OSS 20B accepts 131,072 input tokens compared to GPT-5.3 Chat's 128,000 tokens. GPT OSS 20B can generate longer responses up to 32,768 tokens, while GPT-5.3 Chat is limited to 16,384 tokens.

OpenAI
GPT-5.3 Chat
Input128,000 tokens
Output16,384 tokens
OpenAI
GPT OSS 20B
Input131,072 tokens
Output32,768 tokens
Sat Jul 25 2026 • llm-stats.com

Input Capabilities

Supported data types and modalities

GPT-5.3 Chat supports multimodal inputs, whereas GPT OSS 20B does not.

GPT-5.3 Chat can handle both text and other forms of data like images, making it suitable for multimodal applications.

GPT-5.3 Chat

Text
Images
Audio
Video

GPT OSS 20B

Text
Images
Audio
Video

License

Usage and distribution terms

GPT-5.3 Chat is licensed under a proprietary license, while GPT OSS 20B uses Apache 2.0.

License differences may affect how you can use these models in commercial or open-source projects.

GPT-5.3 Chat

Proprietary

Closed source

GPT OSS 20B

Apache 2.0

Open weights

Release Timeline

When each model was launched

GPT-5.3 Chat was released on 2026-03-04, while GPT OSS 20B was released on 2025-08-05.

GPT-5.3 Chat is 7 months newer than GPT OSS 20B.

GPT-5.3 Chat

Mar 4, 2026

4 months ago

7mo newer
GPT OSS 20B

Aug 5, 2025

11 months ago

Knowledge Cutoff

When training data ends

GPT-5.3 Chat has a documented knowledge cutoff of 2025-08-31, while GPT OSS 20B's cutoff date is not specified.

We can confirm GPT-5.3 Chat's training data extends to 2025-08-31, but cannot make a direct comparison without GPT OSS 20B's cutoff date.

GPT-5.3 Chat

Aug 2025

GPT OSS 20B

—

Provider Availability

GPT-5.3 Chat is available from OpenAI. GPT OSS 20B is available from Novita, Fireworks, Groq, OpenAI.

GPT-5.3 Chat

openai logo
OpenAI
Input Price:Input: $1.75/1MOutput Price:Output: $14.00/1M

GPT OSS 20B

novita logo
Novita
Input Price:Input: $0.05/1MOutput Price:Output: $0.20/1M
fireworks logo
Fireworks
Input Price:Input: $0.10/1MOutput Price:Output: $0.50/1M
groq logo
Groq
Input Price:Input: $0.10/1MOutput Price:Output: $0.50/1M
openai logo
OpenAI
Input Price:Input: $0.10/1MOutput Price:Output: $0.50/1M
* Prices shown are per million tokens

Outputs Comparison

Notice missing or incorrect data?Start an Issue discussion→

Key Takeaways

OpenAI
Supports multimodal inputs
Higher HealthBench score (54.1% vs 42.5%)
Higher HealthBench Hard score (25.9% vs 10.8%)
OpenAI
Larger context window (131,072 tokens)
Less expensive input tokens
Less expensive output tokens
Has open weights

Detailed Comparison

Interactive Arena

Judge for yourself.

Run your own prompts against GPT-5.3 Chat and GPT OSS 20B side-by-side, then vote on the output you prefer.

GPT-5.3 Chat
✓ Preferred
GPT OSS 20B
Open in Playground
AI Model Comparison Table
Feature
OpenAI
GPT-5.3 Chat
OpenAI
GPT OSS 20B

FAQ

Common questions about GPT-5.3 Chat vs GPT OSS 20B.

Which is better, GPT-5.3 Chat or GPT OSS 20B?

GPT-5.3 Chat significantly outperforms across most benchmarks. GPT-5.3 Chat is made by OpenAI and GPT OSS 20B is made by OpenAI. The best choice depends on your use case — compare their benchmark scores, pricing, and capabilities above.

How does GPT-5.3 Chat compare to GPT OSS 20B in benchmarks?

GPT-5.3 Chat scores HealthBench: 54.1%, HealthBench Hard: 25.9%. GPT OSS 20B scores MMLU: 85.3%, CodeForces: 74.3%, GPQA: 71.5%, TAU-bench Retail: 54.8%, HealthBench: 42.5%.

Is GPT-5.3 Chat cheaper than GPT OSS 20B?

GPT OSS 20B is 35.0x cheaper for input tokens. GPT-5.3 Chat costs $1.75/M input and $14.00/M output via openai. GPT OSS 20B costs $0.05/M input and $0.20/M output via novita.

What are the context window sizes for GPT-5.3 Chat and GPT OSS 20B?

GPT-5.3 Chat supports 128K tokens and GPT OSS 20B supports 131K tokens. A larger context window lets you process longer documents, conversations, or codebases in a single request.

What are the main differences between GPT-5.3 Chat and GPT OSS 20B?

Key differences include context window (128K vs 131K), input pricing ($1.75 vs $0.05/M), multimodal support (yes vs no), licensing (Proprietary vs Apache 2.0). See the full comparison above for benchmark-by-benchmark results.

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