OpenAI’s GPT-4o model has taken the world by storm with its impressive multimodal capabilities, including generating images directly within a chat. But how exactly does it create those images? While OpenAI keeps the exact details close to its chest, some clever investigation using browser tools gives us fascinating clues about the GPT-4o image generation process.
One curious user decided to peek behind the curtain by looking at the network traffic while asking GPT-4o to generate images. This “reverse engineering” approach revealed some intriguing details about the steps involved. Let’s dive into what they found and what it might mean.
Table of contents
- GPT-4o Image Generation Process: What the Network Tab Revealed
- Diffusion vs. Autoregressive: Analyzing the GPT-4o Image Generation
- Fewer Steps, More Questions: The ‘Grainy Texture’ Example
- Connecting the Dots: Could OmniGen Be the Key?
- Putting It All Together: What We Think So Far
- The Ongoing Quest to Understand GPT-4o image generation
GPT-4o Image Generation Process: What the Network Tab Revealed
When you ask GPT-4o for an image, like “An image of a happy dog running on the street, studio ghibli style,” it doesn’t just send back the final picture. The network analysis showed that the backend system actually sends intermediate versions of the image as it’s being created.
For the “happy dog” prompt, four distinct images were sent before the final version appeared. These weren’t just random pixels; they showed the image taking shape progressively. This immediately raises questions about the underlying technology.

Diffusion vs. Autoregressive: Analyzing the GPT-4o Image Generation
The big question in image generation often boils down to the core technique used. Two popular methods are diffusion and autoregressive models. Seeing these intermediate steps gives us hints.
The Case for Diffusion-Like Steps
Observing the progression from the first intermediate image to the last revealed something interesting. Early images showed a faint overall structure, and later images added finer details, especially in complex areas like trees.
This process starting with a basic structure and then refining details is very characteristic of diffusion models. These models typically generate a noisy or blurry base and gradually “clean it up,” adding layers of detail.
This was even more apparent with a prompt specifically designed for detail: “create the image of a grainy texture, abstract shape, very extremely highly detailed.” In this case, the intermediate images clearly showed details being layered onto the image, much like how diffusion models work. It resembles techniques like the SDXL refiner model, which was designed specifically to add high-frequency details as a later step in the generation process.

OpenAI’s Stance: An Autoregressive Model?
Here’s where it gets fascinating. OpenAI explicitly stated in its GPT-4o model card that the image generation is not a diffusion model like DALL-E. They claim it’s an “autoregressive model natively embedded within ChatGPT.”
Autoregressive models typically generate content sequentially, piece by piece (like generating text word by word). Applying this concept perfectly to image generation is complex, but it implies a different fundamental approach than diffusion. So, how do we reconcile the diffusion-like intermediate steps we see with OpenAI’s statement?
Fewer Steps, More Questions: The ‘Grainy Texture’ Example
Another puzzle arose with the “grainy texture” prompt. Instead of four intermediate images like the “happy dog,” the analysis only showed three. Why fewer steps?
There could be several reasons:
- Optimization: Perhaps the model recognized the prompt didn’t require as many refinement steps and optimized the process.
- Resource Availability: Maybe it was just a momentary backend constraint, limiting the computational resources (flops) available.
- Techniques like Latent Caching: Advanced techniques might allow reusing parts of the computation, potentially reducing visible steps.
This variability adds another layer to the mystery of the exact GPT-4o image generation pipeline.
Connecting the Dots: Could OmniGen Be the Key?
So, we have diffusion-like observations and an official autoregressive claim. How can both be true? The original investigator pointed towards a recent research paper called “OmniGen” as a potential clue.
OmniGen proposes an architecture that connects the image-handling part (a VAE, common in diffusion models) directly to a Large Language Model (LLM). This allows the model to learn text and images together within a single framework. This approach:
- Is primarily based on transformers, which are known to scale incredibly well with more data and computing power (OpenAI’s specialty).
- Demonstrates few-shot capabilities and emerging properties, matching the versatility we see in GPT-4o.
- Could potentially explain the observed behavior: perhaps an autoregressive transformer controls a process that generates intermediate steps resembling diffusion refinement.
This hybrid approach, leveraging the strengths of both LLMs and image generation techniques within a scalable transformer architecture, fits well with OpenAI’s known strategy: massive scale (data + compute) applied to powerful architectures.
Putting It All Together: What We Think So Far
Based on this network analysis, the GPT-4o image generation process isn’t straightforward. Here’s a summary of the current thinking:
- It’s likely a multi-step process, as evidenced by the intermediate images.
- While OpenAI calls it autoregressive, the observed intermediate steps show characteristics strongly resembling diffusion refinement (adding details progressively).
- Architectures like OmniGen offer a plausible way to combine LLMs and image generation components within a transformer framework, potentially explaining these observations and GPT-4o’s power.
- The exact number of steps might vary based on the prompt or system load.
It could be that the core model is autoregressive in how it plans or sequences the generation, but the actual pixel or latent space manipulation involves steps that look very much like diffusion refinement stages.
The Ongoing Quest to Understand GPT-4o image generation
This peek behind the curtain using simple browser tools offers valuable insights but also highlights how much we still don’t know about state-of-the-art AI models like GPT-4o. The evidence suggests a sophisticated, likely hybrid approach to GPT-4o image generation, potentially leveraging cutting-edge research like OmniGen and OpenAI’s massive scaling capabilities.
Understanding how these powerful models work is crucial as they become more integrated into our digital lives. This investigation is just one piece of the puzzle, and the community’s collective effort will surely uncover more details over time. What are your thoughts on how GPT-4o brings images to life?
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