Grok 4 vs Grok 3: In-Depth AI Model Comparison (2025)

8/13/2025

Grok 4 vs. Grok 3: A Ringside Seat to the AI Evolution

What’s up, everyone? If you’ve been paying even the slightest bit of attention to the AI world, you know that the pace of change is just WILD. It feels like every few months, a new model drops that completely rewrites the rules. And that’s exactly what we’re diving into today: the jump from Grok 3 to Grok 4.

Honestly, when Grok 3 came out in February 2025, it was a solid contender. It was fast, good for everyday tasks, & laid a pretty strong foundation. But then, just a few months later in July, xAI decided to skip 3.5 entirely & dropped Grok 4 on us. And let me tell you, this isn't just a fresh coat of paint. This is a ground-up rebuild. We’re talking a whole new level of performance, a different way of thinking, & capabilities that make Grok 3 look like a relic from a bygone era.

So, let's get into the nitty-gritty. What REALLY separates these two? Is Grok 4 worth the hype (and the price tag)? Let's take a side-by-side look.

The Core Philosophy: A Fundamental Shift in Thinking

Here’s the first thing you need to understand: Grok 3 & Grok 4 are built on fundamentally different philosophies.

Grok 3 was a bit of an all-rounder. It had a "reasoning mode" for tougher questions but also a non-reasoning mode designed for quick, snappy answers. Think of it like a versatile tool that could handle a bunch of different jobs pretty well. It was a generalist, great for quick responses & everyday tasks.

Grok 4, on the other hand, is a specialist. xAI made a bold move & got rid of the non-reasoning mode altogether. Grok 4 is ALWAYS in reasoning mode. This means it's not really built for asking about the weather or finding a nearby coffee shop. It’s designed for deep, complex problem-solving. By focusing all its computational power on analytical depth & accuracy, xAI has positioned Grok 4 as a tool for the heavy lifting – the kind of stuff you'd see in science, math, finance, & engineering.

This is a HUGE deal. It’s a shift from a "jack of all trades" to a "master of one" (or, in this case, a master of complex reasoning). Grok 3 was your helpful assistant; Grok 4 is your PhD-level research partner.

Under the Hood: Architecture & Power

So, how did xAI pull off this massive leap in reasoning? It all comes down to the architecture & the sheer power they're throwing at it.

Grok 3 was already a beast, trained on a massive supercomputer. But Grok 4 is on another planet. It was trained on xAI's "Colossus" supercomputer, which reportedly uses around 200,000 NVIDIA H100 GPUs. The company has said that Grok 4 utilized about 10 times more compute than Grok 3. That's not an incremental update; that's an exponential one.

But it’s not just about more power. Grok 4’s architecture is reportedly a Mixture-of-Experts (MoE) transformer. Think of it like this: instead of one giant brain trying to do everything, an MoE model has a collection of smaller, specialized "expert" networks. When a task comes in, the system intelligently routes it to the most relevant experts. This makes the model more efficient & capable.

And then there's Grok 4 Heavy. This is where things get really futuristic. Grok 4 Heavy is a multi-agent system. Instead of a single model tackling a problem, it spins up several AI agents that work on the same task in parallel. They can work independently, share insights, compare results, & then converge on the best possible answer. It’s like having a study group of brilliant AIs working on your problem. This collaborative approach is what allows it to achieve such incredible results on the most difficult benchmarks.

Grok 3, in comparison, was a single-agent model. It was powerful, but it lacked this collaborative, multi-faceted approach to problem-solving. This architectural evolution is a key reason for Grok 4's superior performance.

The Benchmark Beatdown: Just How Much Better Is It?

Okay, let's talk numbers. Because the benchmarks for Grok 4 are, frankly, insane.

One of the most talked-about is the American Invitational Mathematics Examination (AIME), a notoriously difficult math competition. Grok 4 Heavy reportedly scored a perfect 100% on it. To put that in perspective, Grok 3 scored a very respectable 52.2%. That's a jump from "pretty good at math" to "literally perfect."

Then there's the Graduate-level Physics Question Answering (GPQA) test. Grok 4 scored 87%, while Grok 3 came in at 75.4%. Again, a significant leap in a highly specialized, expert-level domain.

But the one that really turned heads is Humanity's Last Exam (HLE). This is a benchmark designed to be almost impossible, with PhD-level questions across a huge range of subjects.

Grok 4 (without tools) scored 25.4%.
Grok 4 (with tools) jumped to 44.4%.
Grok 4 Heavy pushed that to an incredible 50.7% on the text-only subset.

For comparison, Grok 3's performance wasn't even in the same league. And top models from competitors like Google's Gemini 2.5 Pro were trailing behind at 21.6% (without tools).

It’s important to note that some sources show slightly different numbers, & some benchmarks are still based on internal tests. One source even noted that on a few specific benchmarks, like AIME 2025 & LiveCodeBench, Grok-3 actually outperformed Grok-4 slightly, suggesting that Grok 4's dominance isn't universal across every single metric. However, the overall trend is undeniable: Grok 4, especially the Heavy variant, is setting a new state-of-the-art in complex reasoning.

The Developer Experience: More Than Just a Pretty Interface

For developers, the move from Grok 3 to Grok 4 is a game-changer. Grok 3 provided basic coding help, like simple code snippets & explanations. It was more for beginners. Grok 4, however, is a serious coding assistant.

There's even a specialized Grok 4 Code variant on the way (expected August 2025) that's designed for real-time IDE integration, advanced code generation, & debugging.

A huge part of this is the expanded context window. Grok 3 could handle up to 128,000 tokens. Grok 4 doubles that to 256,000 tokens via the API. What does this mean in practice? A developer could feed an entire source code file into the model to find a bug, or a business could analyze a massive report in one go without having to break it up.

Another major upgrade is native tool use. Grok 4 was trained from the ground up to know when & how to use external tools like a code interpreter or a web browser. It doesn't just generate code; it can run it, test it, & debug it. This is a massive leap over Grok 3's more limited tool integration.

For businesses looking to leverage AI, this is HUGE. Imagine building a customer service solution that can not only understand a customer's problem but also query a database, analyze the results, & provide a concrete solution. This is where platforms like Arsturn come into play. Arsturn helps businesses create custom AI chatbots trained on their own data. With the power of a model like Grok 4, these chatbots could become incredibly sophisticated, providing instant, intelligent support & engaging with website visitors 24/7. The ability to handle complex queries & use tools means customer interactions can be resolved faster & more accurately than ever before.

However, developers migrating from Grok 3 to Grok 4 need to be aware of some API changes. Since Grok 4 is a reasoning-only model, parameters like

presencePenalty

frequencyPenalty

, &

reasoning_effort

are no longer supported & will cause errors.

Multimodality: Seeing is Believing

Grok 3 was primarily a text-based model. It could handle language with the best of them, but that's where its capabilities ended. Grok 4 is a true multimodal AI.

It currently supports text & vision, meaning it can analyze images. You can show it a picture & ask questions about it. But that's just the beginning. The roadmap includes:

Image generation: Coming soon.
Video processing: Expected around October 2025.
Enhanced Voice Mode: An upgraded voice mode, featuring a new, more natural-sounding voice named "Eve," is already here. You can even point your camera at something during a voice chat, & Grok will analyze the scene in real-time.

This is a massive expansion of capabilities. For businesses, this opens up a world of possibilities. A company could use an AI chatbot to help customers troubleshoot a product by having them simply show the issue via their phone's camera.

This is where a solution like Arsturn could become even more powerful. Imagine a business building a no-code AI chatbot with Arsturn, trained on its product manuals & FAQs. With Grok 4's multimodal capabilities, that chatbot could not only answer text-based questions but also analyze images of a broken part or a confusing setup, providing a much more personalized & effective customer experience. This kind of advanced, interactive support can be a major differentiator & significantly boost customer satisfaction & conversions.

Real-Time Data & The X-Factor

One of Grok's unique selling points has always been its integration with X (formerly Twitter). Grok 4 takes this to a whole new level with deep, native integration that pulls in real-time data from X, Tesla, & SpaceX.

While other models can browse the web for current information, Grok 4's direct pipeline to the X firehose gives it an unparalleled, up-to-the-second awareness of public discourse & breaking news. This is a powerful tool for businesses that need to stay on top of trends, monitor brand sentiment, or conduct real-time market analysis.

The Cost of Power: Pricing & Availability

With all this power comes a significant price tag. Grok 3's API pricing was fairly standard, at $3 per million input tokens & $15 per million output tokens. Grok 4's API pricing is the same, but the subscription model is where you see the difference.

Standard Grok 4 access comes with the X Premium+ plan, which is around $30 a month.
SuperGrok Heavy, which gives you access to the most powerful multi-agent version, comes with a hefty $300 per month subscription.

This makes Grok 4 Heavy the most expensive AI chatbot subscription on the market. It's clear that xAI is positioning this as an enterprise-grade tool for researchers, developers, & businesses with deep pockets & a need for cutting-edge performance.

Grok 3, being faster & more affordable, remains the better choice for everyday, general-purpose tasks. But for anyone needing PhD-level reasoning & advanced capabilities, Grok 4 is in a class of its own.

So, What's the Verdict?

The jump from Grok 3 to Grok 4 isn't just an upgrade; it's a redefinition. Grok 3 was a capable, fast, & useful AI assistant. Grok 4 is a specialized, deep-thinking powerhouse.

Here’s a quick breakdown:

Feature	Grok 3	Grok 4
Architecture	Single-agent	Mixture-of-Experts, Multi-agent (Heavy)
Primary Use	Fast, everyday tasks	Complex reasoning, specialized tasks
Context Window	Up to 128k tokens	Up to 256k tokens (API)
Multimodality	Text-only	Text, Vision (Image/Video coming)
Coding	Basic assistance	Advanced, dedicated Code variant
Tool Use	Limited	Native, integrated
Pricing (Heavy)	N/A	$300/month

Ultimately, the choice between them depends entirely on your needs. If you need a quick, responsive AI for general tasks, Grok 3 (or a similar model) is still a great option. But if you're a developer pushing the boundaries of what's possible, a researcher tackling complex problems, or a business looking to build next-generation AI solutions, Grok 4 is the new king of the hill.

The pace of AI development is just staggering, & the evolution from Grok 3 to Grok 4 is a perfect example of that. It's a leap that has pushed the entire industry forward.

Hope this was helpful! Let me know what you think about this crazy AI race. It’s going to be a wild ride.