GPT-5.3-Codex vs GPT-5.5 Pro
A side-by-side comparison of two multimodal models — real specs, pricing, strengths and weaknesses, and a clear verdict on which to choose. Kept current by our agents.
Quick verdict: which should you choose?
Choose GPT-5.3-Codex if you need
- ✓Very large 1.05M-token context for extended multimodal inputs
- ✓Native support for files, images, and text with seamless integration
- ✓Strong reasoning capabilities over very long combined inputs
- ✓General-purpose multimodal tasks beyond narrow coding
Choose GPT-5.5 Pro if you need
- ✓Specialized programming workflows with known 79.41 t/s output speed
- ✓Much lower cost at $14 per million tokens
- ✓400k context sufficient for most coding tasks with diverse inputs
- ✓Predictable performance when input quality is high
Verdict
GPT-5.5 Pro leads for maximum-scale multimodal reasoning with its 1.05M-token context and native file/image/text integration, while GPT-5.3-Codex wins on cost-efficiency and coding specialization at 400k context for $14/M versus $180/M. GPT-5.5 Pro's unknown speed and intelligence metrics leave performance on long inputs unclear compared to Codex's reported 79.41 t/s. Overall, the choice hinges on whether extreme context or programming focus matters more.
GPT-5.3-Codex vs GPT-5.5 Pro: side by side
| Spec | GPT-5.3-Codex | GPT-5.5 Pro | Winner |
|---|---|---|---|
| Intelligence | 44.3 | — | Tie |
| Output speed | 79 t/s | — | Tie |
| Output price | $14.00/1M | $180.00/1M | GPT-5.3-Codex |
| Context | 400K | 1050K | GPT-5.5 Pro |
| Params | — | — | Tie |
| Provider | OpenAI | OpenAI | Tie |
Detailed analysis
Context Window
Winner: GPT-5.5 ProGPT-5.5 Pro provides a 1,050,000-token context window compared to GPT-5.3-Codex's 400,000 tokens. This gives Pro a clear advantage for handling over a million tokens of multimodal data. Codex still offers extensive context but is limited to less than half the scale.
Pricing
Winner: GPT-5.3-CodexGPT-5.3-Codex costs $14 per million tokens while GPT-5.5 Pro costs $180 per million tokens. The large price gap favors Codex for frequent or budget-conscious use. No other cost factors are provided in the data.
Multimodal Capabilities
Winner: GPT-5.5 ProGPT-5.5 Pro emphasizes seamless multimodal integration with native file, image, and text support plus strong reasoning over extended inputs. GPT-5.3-Codex supports diverse input types but is described with a narrower coding focus. Pro lacks audio or video while Codex limitations center on input quality dependency.
Specialization & Speed
Winner: GPT-5.3-CodexGPT-5.3-Codex is explicitly specialized for programming workflows with a reported output speed of 79.41 t/s and intelligence index of 44.3. GPT-5.5 Pro has no speed or intelligence metrics listed and notes potential latency on very long inputs. Codex's narrower focus trades off against Pro's broader multimodal strengths.
GPT-5.3-Codex
Pros
- +Specialized for programming workflows
- +Extensive context handling
- +Support for diverse input types
Cons
- –Narrower focus than general-purpose models
- –Performance tied to input quality
GPT-5.5 Pro
Pros
- +Very large context window
- +Native support for files, images, and text
- +Seamless multimodal integration
Cons
- –High resource use with maximum context
- –No audio or video modalities
- –Potential latency on very long inputs
Summary: GPT-5.3-Codex vs GPT-5.5 Pro
Choose GPT-5.5 Pro when maximum context and broad multimodal reasoning are required despite higher cost. Select GPT-5.3-Codex for coding-focused tasks where speed, lower price, and sufficient 400k context deliver better value. The models serve overlapping but distinct priorities within OpenAI's proprietary lineup.
Frequently asked questions
GPT-5.5 Pro has the larger context at 1,050,000 tokens versus GPT-5.3-Codex at 400,000 tokens.