Grok 4 Fast
xai/grok-4-fastTwo million tokens of context at commodity prices, long-context economics, reset.
Model overview
Context window
2M
tokens
Input price
—
quoted on request
Output price
—
quoted on request
Weekly volume
—
tokens / week
Open weights
No
API only
Capabilities
4
of 11 tags
Description
Grok 4 Fast is a language model from xAI. Webparam does not stock this model yet and can source it on request — tell us what you need it for and we will come back with availability and a price. xAI’s stated focus is real-time-grounded frontier models. The weights are not published, so it is API-only.
Capabilities
- Tool calling
- Calls functions you define and returns their arguments as structured data, the basis of agents.
- JSON mode
- Constrains the response to valid JSON matching a schema you supply.
- Streaming
- Emits tokens as they are generated, so answers appear progressively rather than all at once.
- Long context
- Built for inputs well beyond the mainstream window, whole repositories, archives or corpora.
Strengths & weaknesses
Strengths
- 2M context at workhorse prices
- Fast
- Good tool calling
Weaknesses
- Depth trails Grok 4.1
- Recall softens at extreme depth
Pricing
Free| Rate | Price | Unit |
|---|---|---|
| Input | $0.00 | per 1M tokens |
| Output | — not charged | — |
Free at the point of use; fair-use rate limits apply to the free tier. Illustrative placeholder pricing.
Context window
2Mtokens
covers prompt and response together, so a long input leaves less room for the answer.
Supported features
| Feature | Support |
|---|---|
| Tool calling | Supported |
| JSON mode | Supported |
| Streaming | Supported |
| Vision input | Not supported |
| Audio input | Not supported |
| Long context | Supported |
| Open weights | Not supported |
| Reasoning | Not supported |
| Fine-tunable | Not supported |
| Batch | Not supported |
| Caching | Not supported |
Example use cases
Long-context volume work
2M context at workhorse prices
Archive Q&A
Fast
Cost-tiered routing
Good tool calling
Comparison
| Attribute | Grok 4 Fast | Llama 4 Scout | MiniMax Text 01 |
|---|---|---|---|
| Context window | 2M | 10M | 1M |
| Input price | $0.00 | $0.00 | $0.00 |
| Output price | — not charged | — not charged | — not charged |
| Tool calling | Supported | Supported | Supported |
| JSON mode | Supported | Not supported | Not supported |
| Vision input | Not supported | Not supported | Not supported |
| Open weights | Not supported | Supported | Supported |
| Prompt caching | Not supported | Not supported | Not supported |
Best value in each row is highlighted. Illustrative placeholder data.
Provider information
View xAI →xAI · San Francisco, United States · est. 2023
xAI built one of the largest training clusters in existence and iterated Grok to the frontier at unusual speed. Its models are distinguished by real-time grounding and enormous fast-inference context, Grok 4 Fast's 2M-token window at commodity prices reset long-context economics.
Recent releases
Documentation
Frequently asked questions
Input is billed at $0.00 per 1M tokens, and there is no separate output charge. Every figure on this page is an illustrative placeholder.