GPT-5.3-Codex vs GPT-5.5 Instant
GPT-5.3-Codex (2026) and GPT-5.5 Instant (2026) compare a coding-specialized model against a standalone API model. GPT-5.3-Codex ships a 400k-token context window, while GPT-5.5 Instant ships a 400k-token context window. On pricing, GPT-5.3-Codex costs $1.75/1M input tokens versus $5/1M for the alternative. This page treats the result as workflow and deployment fit, not a universal model winner.
Treat this as a product-type comparison: GPT-5.3-Codex is coding-specialized model, while GPT-5.5 Instant is standalone API model. Choose based on workflow fit before reading any benchmark or price row as decisive.
Decision scorecard
Local evidence first| Signal | GPT-5.3-Codex | GPT-5.5 Instant |
|---|---|---|
| Product type | Coding-specialized model | Standalone API model |
| Best for | custom coding agents, code generation, and tool loops | multimodal apps and tool-calling agents |
| Decision fit | Coding, RAG, and Agents | Coding, RAG, and Agents |
| Context window | 400k | 400k |
| Cheapest output | $14/1M tokens | $30/1M tokens |
| Provider routes | 3 tracked | 1 tracked |
| Shared benchmarks | 0 shared | 0 shared |
Decision tradeoffs
- GPT-5.3-Codex has the lower cheapest tracked output price at $14/1M tokens.
- GPT-5.3-Codex has broader tracked provider coverage for fallback and procurement flexibility.
- GPT-5.3-Codex uniquely exposes Reasoning and Computer use in local model data.
- Local decision data tags GPT-5.3-Codex for Coding, RAG, and Agents.
- GPT-5.5 Instant uniquely exposes Multimodal in local model data.
- Local decision data tags GPT-5.5 Instant for Coding, RAG, and Agents.
Monthly cost at traffic
Estimate token spend from the cheapest tracked input and output route or tier on this page.
GPT-5.3-Codex
$4,900
Cheapest tracked route/tier: OpenRouter
GPT-5.5 Instant
$11,500
Cheapest tracked route/tier: OpenAI API
Estimated monthly gap: $6,600. Batch, cache, alternate speed tiers, and negotiated pricing are excluded from this local estimate.
Switch friction
- Provider overlap exists on OpenAI API; start route-level A/B tests there.
- GPT-5.5 Instant is $16/1M tokens higher on cheapest tracked output pricing, so quality gains need to justify the spend.
- Check replacement coverage for Reasoning and Computer use before moving production traffic.
- GPT-5.5 Instant adds Multimodal in local capability data.
- Provider overlap exists on 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.
- GPT-5.3-Codex adds Reasoning and Computer use in local capability data.
Specs
| Specification | ||
|---|---|---|
| Released | 2026-02-05 | 2026-05-05 |
| Context window | 400k | 400k |
| Parameters | — | — |
| Architecture | Decoder Only | Decoder Only |
| License | Proprietary | Proprietary |
| Openness | Proprietary | Proprietary |
| Commercial use | Commercial use: conditional | Commercial use: conditional |
| Knowledge cutoff | 2025-08 | 2025-08 |
Pricing and availability
| Pricing attribute | GPT-5.3-Codex | GPT-5.5 Instant |
|---|---|---|
| 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 Instant |
|---|---|---|
| Vision | Yes | Yes |
| Multimodal | No | Yes |
| Reasoning | Yes | No |
| Function calling | Yes | Yes |
| Tool use | Yes | Yes |
| Structured outputs | Yes | Yes |
| Code execution | Yes | Yes |
| IDE integration | No | No |
| Computer use | Yes | No |
| Parallel agents | No | No |
Benchmarks
No shared benchmark scores are currently available for this pair.
Deep dive
The capability footprint differs most on multimodal input: GPT-5.5 Instant and reasoning mode: GPT-5.3-Codex. Both models share vision, function calling, tool use, and structured outputs, 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 on the cheapest tracked provider, while GPT-5.5 Instant 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 3 providers versus 1, so concentration risk also matters.
Choose GPT-5.3-Codex when coding workflow support, lower input-token cost, and broader provider choice are central to the workload. Choose GPT-5.5 Instant when coding workflow support are more important. For production, rerun your own prompts through the exact provider, region, and tool stack you plan to ship. This keeps the decision grounded in measurable tradeoffs instead of brand-level assumptions. It also helps separate model capability from provider packaging, which can change cost and latency.
FAQ
Which has a larger context window, GPT-5.3-Codex or GPT-5.5 Instant?
GPT-5.3-Codex supports 400k tokens, while GPT-5.5 Instant 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 Instant?
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 Instant 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 Instant open source?
GPT-5.3-Codex is listed under Proprietary. GPT-5.5 Instant 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 Instant?
Both GPT-5.3-Codex and GPT-5.5 Instant 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 Instant?
GPT-5.5 Instant 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 Instant?
GPT-5.3-Codex is available on OpenRouter, OpenAI API, and Vercel AI Gateway. GPT-5.5 Instant is available on OpenAI API. Provider coverage can affect latency, region availability, compliance posture, and fallback options.
Continue comparing
Last reviewed: 2026-06-19. Data sourced from public model cards and provider documentation.