GPT-5-Nano is the smallest and fastest variant in the GPT-5 system, optimized for developer tools, rapid interactions, and ultra-low latency environments. While limited in reasoning depth compared to its larger counterparts, it retains key …
Model details →OpenAI: GPT-5 Nano vs xAI: Grok 4 Fast
OpenAI: GPT-5 Nano wins on 2 of 6 axes — pricing and capability skew in its favour for most workloads.
Grok 4 Fast is xAI's latest multimodal model with SOTA cost-efficiency and a 2M token context window. It comes in two flavors: non-reasoning and reasoning. Read more about the model on xAI's [news post](http://x.ai/news/grok-4-fast). Reaso…
Model details →Side-by-side comparison
| Capability | OpenAI: GPT-5 Nano | xAI: Grok 4 Fast | Winner |
|---|---|---|---|
| Context window Maximum number of input tokens the model can attend to in a single request. | 400K | 2M | 🏆 xAI: Grok 4 Fast |
| Input price (per 1M) Cost per million input tokens billed by the provider. | $0.05 | $0.20 | 🏆 OpenAI: GPT-5 Nano |
| Output price (per 1M) Cost per million output tokens billed by the provider. | $0.40 | $0.50 | 🏆 OpenAI: GPT-5 Nano |
| Tool / function calling First-class support for emitting structured tool calls. | Yes | Yes | Tie |
| Vision input Accepts image inputs alongside text. | Yes | Yes | Tie |
| Reasoning mode Internal chain-of-thought / extended-thinking support. | Yes | Yes | Tie |
Frequently asked questions
Is OpenAI: GPT-5 Nano better than xAI: Grok 4 Fast?
OpenAI: GPT-5 Nano wins on 2 of 6 axes — pricing and capability skew in its favour for most workloads.
What's the price difference between OpenAI: GPT-5 Nano and xAI: Grok 4 Fast?
Input: $0.05 vs $0.20 per 1M tokens. Output: $0.40 vs $0.50 per 1M tokens.
What context windows do OpenAI: GPT-5 Nano and xAI: Grok 4 Fast support?
OpenAI: GPT-5 Nano supports up to 400K tokens. xAI: Grok 4 Fast supports up to 2M tokens.
Do both OpenAI: GPT-5 Nano and xAI: Grok 4 Fast support tool calling?
OpenAI: GPT-5 Nano: yes. xAI: Grok 4 Fast: yes.