GPT-5.3-Codex vs GPT-5.5
GPT-5.3-Codex (2026) and GPT-5.5 (2026) are agentic coding models from OpenAI. GPT-5.3-Codex ships a 400K-token context window, while GPT-5.5 ships a 1.1M-token context window. On SWE-bench Verified, GPT-5.5 leads by 3.7 pts. On pricing, GPT-5.3-Codex costs $1.75/1M input tokens versus $5/1M for the alternative. This comparison covers specs, pricing, capabilities, benchmarks, provider availability, and production fit. It focuses on practical selection signals rather than broad model-family marketing.
GPT-5.3-Codex is ~186% cheaper at $1.75/1M; pay for GPT-5.5 only for coding workflow support.
Decision scorecard
Local evidence first| Signal | GPT-5.3-Codex | GPT-5.5 |
|---|---|---|
| Decision fit | Coding, RAG, and Agents | Coding, RAG, and Agents |
| Context window | 400K | 1.1M |
| Cheapest output | $14/1M tokens | $30/1M tokens |
| Provider routes | 2 tracked | 2 tracked |
| Shared benchmarks | 2 rows | SWE-bench Verified leader |
Decision tradeoffs
- GPT-5.3-Codex has the lower cheapest tracked output price at $14/1M tokens.
- Local decision data tags GPT-5.3-Codex for Coding, RAG, and Agents.
- GPT-5.5 leads the largest shared benchmark signal on SWE-bench Verified by 3.7 points.
- GPT-5.5 has the larger context window for long prompts, retrieval packs, or transcript analysis.
- GPT-5.5 uniquely exposes Multimodal in local model data.
- Local decision data tags GPT-5.5 for Coding, RAG, and Agents.
Monthly cost at traffic
Estimate token spend from the cheapest tracked input and output prices on this page.
GPT-5.3-Codex
$4,900
Cheapest tracked route: OpenRouter
GPT-5.5
$11,500
Cheapest tracked route: OpenAI API
Estimated monthly gap: $6,600. Batch, cache, and negotiated pricing are excluded from this local estimate.
Switch friction
- Provider overlap exists on OpenAI API and OpenRouter; start route-level A/B tests there.
- GPT-5.5 is $16/1M tokens higher on cheapest tracked output pricing, so quality gains need to justify the spend.
- GPT-5.5 adds Multimodal in local capability data.
- Provider overlap exists on OpenRouter and OpenAI API; start route-level A/B tests there.
- GPT-5.3-Codex is $16/1M tokens lower on cheapest tracked output pricing before cache, batch, or negotiated discounts.
- Check replacement coverage for Multimodal before moving production traffic.
Specs
| Specification | ||
|---|---|---|
| Released | 2026-02-05 | 2026-04-23 |
| Context window | 400K | 1.1M |
| Parameters | — | — |
| Architecture | decoder only | decoder only |
| License | Proprietary | Proprietary |
| Knowledge cutoff | 2025-08 | 2025-12 |
Pricing and availability
| Pricing attribute | GPT-5.3-Codex | GPT-5.5 |
|---|---|---|
| Input price | $1.75/1M tokens | $5/1M tokens |
| Output price | $14/1M tokens | $30/1M tokens |
| Providers |
Capabilities
| Capability | GPT-5.3-Codex | GPT-5.5 |
|---|---|---|
| Vision | Yes | Yes |
| Multimodal | No | Yes |
| Reasoning | Yes | Yes |
| Function calling | Yes | Yes |
| Tool use | Yes | Yes |
| Structured outputs | Yes | Yes |
| Code execution | Yes | Yes |
Benchmarks
| Benchmark | GPT-5.3-Codex | GPT-5.5 |
|---|---|---|
| SWE-bench Verified | 85.0 | 88.7 |
| SWE-bench Pro | 56.8 | 58.6 |
Deep dive
On shared benchmark coverage, SWE-bench Verified has GPT-5.3-Codex at 85 and GPT-5.5 at 88.7, with GPT-5.5 ahead by 3.7 points; SWE-bench Pro has GPT-5.3-Codex at 56.8 and GPT-5.5 at 58.6, with GPT-5.5 ahead by 1.8 points. The largest visible gap is 3.7 points on SWE-bench Verified, which matters most when that benchmark mirrors your workload. Treat isolated benchmark wins as directional, because provider routing, prompt style, and tool access can move real application results.
The capability footprint differs most on multimodal input: GPT-5.5. Both models share vision, reasoning mode, function calling, and tool use, so the practical split is not just feature count. Use those differences to decide whether the page is about raw model quality, agentic coding support, multimodal ingestion, or predictable structured API behavior.
For cost, GPT-5.3-Codex lists $1.75/1M input and $14/1M output tokens, while GPT-5.5 lists $5/1M input and $30/1M output tokens on the cheapest tracked provider. A 70/30 input-output blend puts GPT-5.3-Codex lower by about $7.08 per million blended tokens. Availability is 2 providers versus 2, so concentration risk also matters.
Choose GPT-5.3-Codex when coding workflow support and lower input-token cost are central to the workload. Choose GPT-5.5 when coding workflow support and larger context windows are more important. For production, rerun your own prompts through the exact provider, region, and tool stack you plan to ship.
FAQ
Which has a larger context window, GPT-5.3-Codex or GPT-5.5?
GPT-5.5 supports 1.1M tokens, while GPT-5.3-Codex supports 400K tokens. That gap matters most for long documents, large codebases, retrieval-heavy agents, and conversations where earlier context must remain visible. Use this as a quick comparison signal, then confirm the provider-specific limits before committing to production.
Which is cheaper, GPT-5.3-Codex or GPT-5.5?
GPT-5.3-Codex is cheaper on tracked token pricing. GPT-5.3-Codex costs $1.75/1M input and $14/1M output tokens. GPT-5.5 costs $5/1M input and $30/1M output tokens. Provider discounts or batch pricing can still change the final bill.
Is GPT-5.3-Codex or GPT-5.5 open source?
GPT-5.3-Codex is listed under Proprietary. GPT-5.5 is listed under Proprietary. License labels affect whether you can self-host, redistribute weights, or rely only on hosted APIs, so confirm the upstream license before deployment.
Which is better for vision, GPT-5.3-Codex or GPT-5.5?
Both GPT-5.3-Codex and GPT-5.5 expose vision. The better choice depends on benchmark fit, context budget, pricing, and whether your provider route exposes the same capability surface. Use this as a quick comparison signal, then confirm the provider-specific limits before committing to production.
Which is better for multimodal input, GPT-5.3-Codex or GPT-5.5?
GPT-5.5 has the clearer documented multimodal input signal in this comparison. If multimodal input is mission-critical, validate it against the provider endpoint because model-level support and API-level exposure can differ.
Where can I run GPT-5.3-Codex and GPT-5.5?
GPT-5.3-Codex is available on OpenRouter and OpenAI API. GPT-5.5 is available on OpenAI API and OpenRouter. Provider coverage can affect latency, region availability, compliance posture, and fallback options. Use this as a quick comparison signal, then confirm the provider-specific limits before committing to production.
Continue comparing
Last reviewed: 2026-05-11. Data sourced from public model cards and provider documentation.