GPT-5.5 Instant vs Grok 4.3
GPT-5.5 Instant (2026) and Grok 4.3 (2026) are frontier reasoning models from OpenAI and xAI. GPT-5.5 Instant ships a 400K-token context window, while Grok 4.3 ships a 1M-token context window. On pricing, Grok 4.3 costs $1.25/1M input tokens versus $1.5/1M 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-5.5 Instant is safer overall; choose Grok 4.3 when reasoning depth matters.
Specs
| Specification | ||
|---|---|---|
| Released | 2026-05-05 | 2026-04-30 |
| Context window | 400K | 1M |
| Parameters | — | ~0.5T |
| Architecture | decoder only | - |
| License | Proprietary | Proprietary |
| Knowledge cutoff | 2025-08 | - |
Pricing and availability
| Pricing attribute | GPT-5.5 Instant | Grok 4.3 |
|---|---|---|
| Input price | $1.5/1M tokens | $1.25/1M tokens |
| Output price | $6/1M tokens | $2.5/1M tokens |
| Providers |
Capabilities
| Capability | GPT-5.5 Instant | Grok 4.3 |
|---|---|---|
| Vision | Yes | Yes |
| Multimodal | Yes | Yes |
| Reasoning | No | Yes |
| Function calling | Yes | Yes |
| Tool use | Yes | Yes |
| Structured outputs | Yes | Yes |
| Code execution | Yes | No |
Benchmarks
No shared benchmark rows are currently sourced for this pair.
Deep dive
The capability footprint differs most on reasoning mode: Grok 4.3 and code execution: GPT-5.5 Instant. Both models share vision, multimodal input, 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-5.5 Instant lists $1.5/1M input and $6/1M output tokens, while Grok 4.3 lists $1.25/1M input and $2.5/1M output tokens on the cheapest tracked provider. A 70/30 input-output blend puts Grok 4.3 lower by about $1.22 per million blended tokens. Availability is 1 providers versus 2, so concentration risk also matters.
Choose GPT-5.5 Instant when coding workflow support are central to the workload. Choose Grok 4.3 when reasoning depth, larger context windows, and lower input-token cost 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-5.5 Instant or Grok 4.3?
Grok 4.3 supports 1M 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.
Which is cheaper, GPT-5.5 Instant or Grok 4.3?
Grok 4.3 is cheaper on tracked token pricing. GPT-5.5 Instant costs $1.5/1M input and $6/1M output tokens. Grok 4.3 costs $1.25/1M input and $2.5/1M output tokens. Provider discounts or batch pricing can still change the final bill.
Is GPT-5.5 Instant or Grok 4.3 open source?
GPT-5.5 Instant is listed under Proprietary. Grok 4.3 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-5.5 Instant or Grok 4.3?
Both GPT-5.5 Instant and Grok 4.3 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-5.5 Instant or Grok 4.3?
Both GPT-5.5 Instant and Grok 4.3 expose multimodal input. 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.
Where can I run GPT-5.5 Instant and Grok 4.3?
GPT-5.5 Instant is available on OpenAI API. Grok 4.3 is available on xAI Console 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.