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. Reasoning can be enabled/disabled using the reasoning enabled parameter in the API. Learn more in our docs

What is the context length of Grok 4 Fast?

Grok 4 Fast has a 2,000,000 token context window.

What inputs and outputs does Grok 4 Fast support?

Grok 4 Fast accepts text, images, and files such as PDFs as input and returns text.

What other text models does SpaceXAI have?

Grok 4.7, Grok 4.6, Grok 4.5 and 4 more are other text models from SpaceXAI.

When was Grok 4 Fast released?

Grok 4 Fast was released on September 19, 2025. Its knowledge cutoff is September 30, 2025.

Grok 4 Fast - API Pricing & Benchmarks

Grok STT 2.0

Grok STT 2.0 is a speech-to-text model from SpaceXAI and the successor to Grok STT 1.0. It is suited for transcription workloads that need word-level timestamps, optional speaker diarization, and multichannel audio.

Transcription$0.000028/second

Grok Imagine Video 1.5 Lite

Grok Imagine Video 1.5 Lite is a faster, lower-cost video generation model from SpaceXAI, distilled from Grok Imagine Video 1.5. It supports text-to-video and image-to-video, trading some quality for speed and price. 1080p output is rendered at 720p and upscaled.

Videofrom $0.02/second

Grok 4.7

Grok 4.7 is SpaceXAI's flagship model for coding, agentic tasks, and knowledge work, succeeding Grok 4.6. It is particularly strong at long-running software engineering tasks, verifying its own work, and managing long context, and it improves on its predecessor at professional knowledge work such as drafting documents and presentations.

The model was trained with a longer reinforcement learning run weighted toward problems that take many hours to complete, and natively understands the Grok Bot harness for conversational tasks. It ships with a new safeguard stack that pairs strong jailbreak resistance with low refusal rates for legitimate cybersecurity and biology work. SpaceXAI's reported benchmark results use the xhigh reasoning effort.

Text500K context$2 / $6

Grok 4.7 (batch)

Grok 4.7 is SpaceXAI's flagship model for coding, agentic tasks, and knowledge work, succeeding Grok 4.6. It is particularly strong at long-running software engineering tasks, verifying its own work, and managing long context, and it improves on its predecessor at professional knowledge work such as drafting documents and presentations.

The model was trained with a longer reinforcement learning run weighted toward problems that take many hours to complete, and natively understands the Grok Bot harness for conversational tasks. It ships with a new safeguard stack that pairs strong jailbreak resistance with low refusal rates for legitimate cybersecurity and biology work. SpaceXAI's reported benchmark results use the xhigh reasoning effort.

Text500K context$1.60 / $4.80

Grok 4.6

Grok 4.6 is a model from SpaceXAI with frontier performance on coding, knowledge work, and STEM. It is succeeded by Grok 4.7.

Text500K context$2 / $6

Grok 4.6 (batch)

Grok 4.6 is a model from SpaceXAI with frontier performance on coding, knowledge work, and STEM. It is succeeded by Grok 4.7.

Text500K context$1.60 / $4.80

Grok Imagine Image 2.0

Grok Imagine Image 2.0 is an image generation and editing model from xAI. It is suited for creating images from text prompts and editing images from references, with low and medium quality modes.

Imagefrom $0.04/image

Grok STT 1.0

Grok STT is SpaceXAI's speech-to-text model, available via the REST /v1/stt endpoint. It supports transcription with word-level timestamps, optional speaker diarization, and multichannel audio.

Transcription$0.000028/second

Grok Imagine Video 1.5

Grok Imagine Video 1.5 is a video generation model from SpaceXAI. It creates videos from text prompts, with an optional starting image to guide the scene. It can direct subject and camera motion, pacing, atmosphere, and physical behavior while maintaining visual continuity, and can generate synchronized sound effects, ambience, and dialogue.

Videofrom $0.08/second

Grok 4.5

Grok 4.5 is a model from SpaceXAI with frontier performance on coding, knowledge work, and STEM.

Text500K context$2 / $6

Grok Latest

This model always redirects to the latest Grok model from xAI.

Text500K context

Grok Build 0.1

Grok Build 0.1 is SpaceXAI’s fast coding model trained specifically for agentic software engineering workflows. It supports text and image inputs with text output, and is optimized for interactive coding agents, tool use, and multi-step development tasks. The model powers SpaceXAI’s Grok Build CLI and features a 256K context window with no text output limit, making it well suited for long-horizon coding and automation workflows. Currently in early access.

Text256K context$1 / $2

Grok Imagine Video

Grok Imagine Video is SpaceXAI's fast, text-, image-, and reference-conditioned video generation model. It produces short videos (1–15 seconds, 24 fps) at 480p or 720p across seven aspect ratios - 1:1, 16:9, 9:16, 4:3, 3:4, 3:2, and 2:3.

The model supports three generation modes: text-to-video from a prompt alone, image-to-video that animates a still input, and reference-to-video that grounds the output in up to seven reference images for consistent characters, styles, or settings.

Videofrom $0.05/second

Grok Imagine Image Quality

Grok Imagine Image Quality is SpaceXAI's fast, high-fidelity image generation and editing model. It accepts text prompts and optional reference images, producing photorealistic outputs at 1K or 2K across a range of aspect ratios, including flexible adjustment of reference images.

The model emphasizes realistic detail — natural lighting and physics, accurate textures, and consistent rendering of named entities such as brands, public figures, and specific locations. It supports clean multilingual text rendering inside images, making it the top choice for posters, packaging, ads, menus, and social graphics. When given reference images, it preserves identity and structure for product placement, brand-aligned variations, and character continuity across scenes.

Image

Grok Voice TTS 1.0

Grok Voice TTS 1.0 is a text-to-speech model from SpaceXAI. It converts text into spoken audio across 20+ languages with automatic language detection, and offers five built-in voices (Eve, Ara, Rex, Sal, Leo) covering a range of tones. Inline speech tags allow control over pauses, emphasis, pitch, speed, and vocal style. Output is available in MP3, WAV, PCM, μ-law, and A-law formats at sample rates from 8 kHz to 48 kHz, with up to 15,000 characters per request.

Speech$15/M characters

Grok 4.3

Grok 4.3 is a reasoning model from SpaceXAI. It accepts text and image inputs with text output, and is suited for agentic workflows, instruction-following tasks, and applications requiring high factual accuracy. Reasoning can be configured between none/low/medium/high (default low) effort levels.

It supports a 1 million token context window with no output token limit, making it well-suited for long-document analysis, deep research, and multi-step agentic tasks. Pricing is tiered: requests exceeding 200k total tokens are billed at a higher rate.

Text1M context$1.25 / $2.50

Grok 4.3 (batch)

Grok 4.3 is a reasoning model from SpaceXAI. It accepts text and image inputs with text output, and is suited for agentic workflows, instruction-following tasks, and applications requiring high factual accuracy. Reasoning can be configured between none/low/medium/high (default low) effort levels.

It supports a 1 million token context window with no output token limit, making it well-suited for long-document analysis, deep research, and multi-step agentic tasks. Pricing is tiered: requests exceeding 200k total tokens are billed at a higher rate.

Text1M context$1 / $2

Grok 4.20 Multi-Agent

Grok 4.20 Multi-Agent is a variant of SpaceXAI’s Grok 4.20 designed for collaborative, agent-based workflows. Multiple agents operate in parallel to conduct deep research, coordinate tool use, and synthesize information across complex tasks.

Reasoning effort behavior:

Text2M context$1.25 / $2.50

Grok 4.20

Grok 4.20 is a reasoning model from SpaceXAI with industry-leading speed and agentic tool calling capabilities. It combines the lowest hallucination rate on the market with strict prompt adherance, delivering consistently precise and truthful responses.

Reasoning can be enabled/disabled using the reasoning enabled parameter in the API. Learn more in our docs

Text2M context$1.25 / $2.50

Grok 4.20 Multi-Agent Beta

Grok 4.20 Multi-Agent Beta is a variant of xAI’s Grok 4.20 designed for collaborative, agent-based workflows. Multiple agents operate in parallel to conduct deep research, coordinate tool use, and synthesize information across complex tasks.

Reasoning effort behavior:

Text2M context

xAI: Grok 4 Fast

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Frequently asked questions

What is Grok 4 Fast?

What is the context length of Grok 4 Fast?

What inputs and outputs does Grok 4 Fast support?

What other text models does SpaceXAI have?

When was Grok 4 Fast released?

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