The Grok 4.3 xAI API release is now live across the xAI platform, formalizing the API launch of the model that first hit grok.com as a consumer beta on April 17. Grok 4.3 ships with a 1M-token context window, native video input, built-in reasoning, and aggressive pricing — paired with two new companion APIs (Voice and Imagine) that round out xAI’s developer-facing platform. The model ranks #1 on agentic tool calling and instruction following per Artificial Analysis benchmarks, despite trailing GPT-5.5 and Claude Opus 4.7 on overall intelligence index scores. For developers building agentic workflows on a budget, the Grok 4.3 xAI API is a credible competitor at meaningfully lower cost than the frontier-priced alternatives.
What’s actually new
The Grok 4.3 xAI API release on May 5, 2026 brings three meaningful changes. First, the model itself: Grok 4.3 scores 53 on the Artificial Analysis Intelligence Index (vs Grok 4.20’s prior generation), with notable improvements on agentic tool calling, instruction following, and specific verticals like case law (#1 on CaseLaw v2) and corporate finance (#1 on CorpFin). The 1M-token context window is competitive with the frontier; native video input is differentiated.
Second, the pricing. xAI positioned Grok 4.3 as aggressively cheap — meaningfully below GPT-5.5 and Claude Opus 4.7 per million tokens. For high-volume workloads where capability matters more than the absolute top of the leaderboard, the cost differential is substantial. xAI is explicitly competing on price-performance rather than raw capability.
Third, the companion APIs. The Voice API enables real-time speech conversations and voice cloning with low latency. The Imagine API generates images and video with prompts. Together, Grok 4.3 + Voice + Imagine give developers a unified multimodal stack from a single vendor — closing the feature gap with OpenAI’s combined text+image+voice offerings and Anthropic’s multimodal Claude.
The strategic context for the Grok 4.3 xAI API. Following the March 2026 SpaceXAI merger that folded Grok into SpaceX’s broader operations, xAI’s API roadmap has been on watch. The May 5 launch confirms the product team is still shipping aggressively despite the corporate restructure. The combination of competitive capability, distinctive features (1M context, video input), and aggressive pricing positions Grok as a serious option for developers who previously defaulted to OpenAI or Anthropic without considering xAI.
Why Grok 4.3 xAI API matters
- Price-performance is the differentiator. Grok 4.3 isn’t trying to beat GPT-5.5 or Claude Opus 4.7 on the intelligence leaderboard. It’s competing on cost. For workloads where capability is sufficient and cost dominates, Grok 4.3 has a real value proposition.
- Agentic tool calling leadership. Grok 4.3 tops Artificial Analysis leaderboards on agentic tool calling and instruction following. For developers building AI agents that orchestrate many tool calls (the dominant 2026 use case), tool-call accuracy matters more than abstract reasoning benchmarks.
- 1M-token context and video input. The context window matches the frontier; native video input is rare. For document-heavy workloads and video analysis use cases, Grok 4.3 offers capabilities that some competitors don’t.
- Voice and Imagine APIs round out the stack. xAI now offers text, voice, image, and video APIs in a single platform with unified billing and identity. The simplification matters for teams building multimodal products.
- SpaceXAI corporate context is positive, not negative. The merger raised questions about xAI’s product roadmap; the May 5 launch shows continued execution. Combined with reported large compute purchases, xAI is investing aggressively in AI infrastructure.
- The frontier-model market is now four-vendor. OpenAI, Anthropic, Google, and xAI all ship competitive frontier-class models with full multimodal API stacks. Developers genuinely choose; default-vendor positions are eroding.
How to use Grok 4.3 xAI API today
The API is available now to developers with xAI accounts. Getting started is similar to OpenAI or Anthropic’s developer flows.
- Sign up at api.x.ai or via the xAI developer console. New accounts include limited free credits to test; paid usage charges based on token consumption.
- Generate an API key from the console. Store it securely (environment variable, secrets manager); never commit to code repositories.
- Install xAI’s SDK or use HTTP requests directly. The Python SDK is the most-documented; HTTP works with any language.
- Make your first call. The API contract follows the OpenAI-compatible chat-completions format — most code that works with OpenAI works with Grok 4.3 with minimal changes.
- For Voice or Imagine APIs, refer to their specific endpoints. Each has its own input schema; the SDKs cover both.
# Python example using the OpenAI-compatible SDK
pip install openai # xAI uses OpenAI-compatible API
import openai
client = openai.OpenAI(
api_key="xai-your-key-here",
base_url="https://api.x.ai/v1",
)
response = client.chat.completions.create(
model="grok-4-3",
max_tokens=1024,
messages=[
{"role": "user", "content": "Summarize Grok 4.3's key features in two sentences."}
],
)
print(response.choices[0].message.content)
# Tool calling (the area where Grok 4.3 leads)
tools = [{
"type": "function",
"function": {
"name": "get_weather",
"description": "Get current weather for a location",
"parameters": {
"type": "object",
"properties": {
"location": {"type": "string", "description": "City name"}
},
"required": ["location"]
}
}
}]
response = client.chat.completions.create(
model="grok-4-3",
messages=[{"role": "user", "content": "What's the weather in San Francisco?"}],
tools=tools,
)
# Grok 4.3 handles tool calls with high accuracy per benchmarksFor video input, the API supports passing video URLs or base64-encoded video in the messages array. The 1M-token context lets you analyze long-form video content (hours of meetings, long instructional content) in single API calls.
# Video input example
response = client.chat.completions.create(
model="grok-4-3",
messages=[{
"role": "user",
"content": [
{"type": "text", "text": "Summarize the key points of this meeting"},
{"type": "video_url", "video_url": {"url": "https://example.com/meeting.mp4"}},
]
}],
)
print(response.choices[0].message.content)
# For Voice API (real-time conversation)
# Uses a different endpoint and WebSocket-based protocol
# See xAI docs for current details
# For Imagine API (image/video generation)
import requests
r = requests.post(
"https://api.x.ai/v1/imagine/generate",
headers={"Authorization": "Bearer xai-your-key"},
json={"prompt": "A photorealistic image of a sunset over mountains",
"size": "1024x1024"}
)
print(r.json()["data"][0]["url"])How Grok 4.3 compares to the frontier alternatives
The May 2026 frontier-API landscape now has four major options. Each has distinctive strengths.
| Model | Context | Multimodal Inputs | Intelligence Index | Distinguishing Strength |
|---|---|---|---|---|
| GPT-5.5 (OpenAI) | 2M tokens | Text, image, audio | 60 | Top overall intelligence; broad ecosystem |
| Claude Opus 4.7 (Anthropic) | 1M tokens | Text, image, video | 57 | Code reasoning; agentic workflows; long-context |
| Gemini 3.1 Pro (Google) | 2M tokens | Text, image, audio, video | 57 | Multimodal breadth; native Google integration |
| Grok 4.3 (xAI) | 1M tokens | Text, image, video | 53 | Agentic tool calling; price-performance |
The pricing differential is where Grok 4.3 makes its case. xAI’s pricing positions Grok 4.3 meaningfully below frontier alternatives — typical per-million-token costs that are 30-50% lower than GPT-5.5 or Claude Opus 4.7. For workloads with high token volume (RAG pipelines, agentic loops, batch document processing), the cost savings compound into meaningful budget differences.
The capability gap between Grok 4.3 (intelligence index 53) and the top tier (57-60) matters for some use cases and not others. For complex reasoning, coding assistance, mathematical proofs — pick a higher-tier model. For agentic tool use, instruction following, business document processing — Grok 4.3 is competitive or leading. Match the model to the use case rather than defaulting to the highest benchmark.
What’s next
Three threads to watch over the next 60-90 days. First, xAI’s roadmap delivery. Reports indicate seven xAI models are in active training; Grok 5 at 10 trillion parameters is the rumored next major release. Whether xAI sustains the aggressive release cadence post-SpaceXAI merger will signal the organization’s product velocity.
Second, OpenAI and Anthropic competitive responses. Both vendors traditionally compete on capability at the top of the leaderboard; Grok 4.3’s price-aggressive positioning may pressure pricing decisions across the AI API market. Watch for cost reductions on existing frontier models, new mid-tier options, or unbundled pricing for specific workloads.
Third, the developer adoption story. The Grok 4.3 xAI API has the technical credentials to attract developers from competitors; whether developers actually switch depends on platform stickiness (existing OpenAI/Anthropic integrations), procurement preferences, and trust in xAI’s continued execution. Adoption metrics in the next 90 days will reveal whether the price-performance pitch translates to market share movement.
For developers building agentic workflows, Grok 4.3 is worth evaluating against your current stack. The tool-calling benchmarks suggest material accuracy improvements for agent loops; the cost savings could change unit economics. Spin up an account; run your real use cases through both Grok 4.3 and your current model; compare quality, latency, and cost. The evaluation effort is bounded (days, not weeks); the potential upside is meaningful.
Frequently Asked Questions
How much does the Grok 4.3 xAI API cost?
xAI positions Grok 4.3 at aggressive price points below frontier competitors. Specific pricing is on the xAI developer console; expect roughly 30-50% lower than GPT-5.5 or Claude Opus 4.7 per million tokens. For high-volume workloads, the cost savings can be material.
Is Grok 4.3 OpenAI-API compatible?
Yes for the core chat-completions endpoint. Code using the OpenAI SDK works with Grok 4.3 by changing the base URL and model name. The compatibility makes migration testing inexpensive — set up a parallel client and compare.
What’s the difference between Grok 4.3 and Grok 4.20?
Grok 4.3 is the next generation after Grok 4.20 (xAI’s January 2026 release). Improvements: 300+ Elo gain on GDPval-AA benchmark; better tool calling and instruction following; refined reasoning; ranked #1 on case law and corporate finance verticals. The version numbering (4.3 after 4.20) is xAI’s unusual scheme; numerically 4.3 follows 4.20.
What’s the Voice API capable of?
Real-time speech-to-text and text-to-speech with low latency, plus voice cloning. The API is designed for conversational agents — phone-style interactions, voice assistants, interactive applications. Latency is competitive with OpenAI’s Realtime API.
What’s the Imagine API capable of?
Image generation from text prompts (similar to DALL-E or Midjourney via API); video generation in shorter form. Specific resolutions and durations depend on the plan tier; check xAI docs for current capabilities.
How does Grok 4.3 handle reasoning vs frontier alternatives?
Grok 4.3 has built-in reasoning (similar to OpenAI’s o-series and Anthropic’s extended thinking). It performs well on agentic tool use and instruction following but trails on raw intelligence index benchmarks (53 vs GPT-5.5’s 60). For most enterprise workloads, the difference is small; for cutting-edge research or hardest reasoning tasks, the frontier alternatives still lead.
Can I use Grok 4.3 for commercial applications?
Yes. The xAI API terms of service permit commercial use under standard terms. Enterprise contracts with additional commitments (data residency, dedicated capacity, custom SLAs) are available for larger customers. Review the current terms on xAI’s website for specifics.
What about Grok 4.3 on Microsoft Azure or AWS Bedrock?
As of mid-May 2026, Grok 4.3 is available directly via xAI’s API and grok.com. Cloud-provider integrations (Azure, AWS Bedrock, Google Vertex AI) haven’t been announced for Grok 4.3 specifically. Watch for cloud platform announcements; they typically follow API GA by months.