Grok 4.3

About xAI

Founded 2023 · Palo Alto, USA

xAI was founded in March 2023 by Elon Musk together with researchers from DeepMind, OpenAI, Google Research, Microsoft Research and Tesla including Igor Babuschkin and Tony Wu. The company's stated mission is to build maximally truth-seeking AI. Its flagship product is Grok, an LLM-based assistant deeply integrated into X (formerly Twitter) and available via a standalone app and API. Grok 1 weights were released under Apache 2.0 in November 2023 (314B-parameter MoE), Grok 1.5 added 128K context and vision in early 2024, Grok 2 shipped in mid-2024, Grok 3 launched in February 2025 trained on the Colossus supercluster, Grok 4 in mid-2025, and the Grok 4.x line in 2025-2026 culminating in Grok 4.3 on May 1, 2026. xAI raised over $20 billion across multiple rounds with backers including Andreessen Horowitz, Sequoia, Valor Equity, Lightspeed and Saudi funds. The company operates the Colossus cluster in Memphis, the world's largest dedicated AI training site.

Architecture

Decoder-only Transformer (frontier reasoning, always-on test-time compute)

Grok 4.3 was released May 1, 2026 as xAI's frontier model. It is the direct successor to Grok 4 (mid-2025) and Grok 4.20 (early 2026) and follows the same training recipe at significantly larger scale: pretraining on the expanded Colossus supercluster in Memphis (now exceeding 300,000 GPUs), with a multi-trillion-token mixture of web text, code, scientific papers, math content and the continuously growing feed of public posts on the X platform. Post-training relies heavily on large-scale reinforcement learning against verifiable rewards for math, coding and tool-use trajectories. Grok 4.3 ships with always-on reasoning (test-time thinking is no longer optional - the model always reasons before answering) and an upgraded DeepSearch agent that performs multi-step web and X-platform retrieval. The context window jumps to 1M tokens. xAI positions Grok 4.3 as competitive with GPT-5.4 and Gemini 3.1 Pro on math and science benchmarks, with the differentiators being real-time access to X data, a lower refusal rate, and the most generous free-tier API credits of any major provider ($175/month).

Parameters

Undisclosed (estimated multi-hundred billion parameters, likely sparse MoE)

Context

1,000,000 tokens

Capabilities

• 1M token context window with vision input
• Always-on test-time reasoning
• Upgraded DeepSearch agent for X + web retrieval
• Trained on 300K+ GPU Colossus cluster
• Strong AIME, GPQA, ARC-AGI and SWE-bench scores
• Vision input for images and screenshots
• Function calling and structured JSON output
• Native integration with X timeline and DMs
• Available via xAI API, X Premium+ and the Grok mobile app
• Real-time fresh data through built-in retrieval
• $175/month free API credits via data-sharing programme
• Best for: agentic research, real-time question answering, math/code reasoning, X-platform assistants.

Training & license

Multi-trillion-token pretraining mixture of web text, code, math, scientific papers and X public posts. Knowledge cutoff updated continuously through retrieval. Post-training applies RLHF and large-scale reinforcement learning against verifiable rewards on math, code and tool-use tasks.

License: Proprietary commercial license via xAI API, X Premium+ and the Grok app. Weights not publicly released for Grok 2 onwards.

Safety testing: xAI publishes a risk-evaluation summary on x.ai. The model is intentionally less restrictive than competitor frontier models; external evaluations are limited.