Stable Diffusion webUI vs ComfyUI: A Comparison from Their Origins

Introduction

Hey there, I’m Easygoing!

In this post, I’ll be diving into a comparison of two leading image generation AI tools, tracing their evolution from the beginning.

Stable Diffusion webUI vs. ComfyUI

The two dominant players in the image generation AI space today are Stable Diffusion webUI and ComfyUI.

When starting with local image generation, choosing the right tool can be daunting. Let’s break it down by exploring when these tools emerged and the context behind their development.

A Brief History of Image Generation AI Tools

First, let’s look at the timeline of when key image generation AI tools were introduced.

gantt
    title AI Image Generation Tools
    dateFormat YYYY-MM-DD
    tickInterval 6month

    section AI Models

        Stable Diffusion 1 : milestone, m1, 2022-08-22,
        Stable Diffusion XL : milestone, m2, 2023-07-26,
        Stable Diffusion 3 : milestone, m3, 2024-06-12,
        Flux.1 : milestone, m4, 2024-08-01,
        HiDream : milestone, m5, 2025-04-06,

    section Stable Diffusion<br>webUI
        A1111 : done, a1, 2022-08-22, 2024-07-27
        Forge : a2, 2024-01-14, 2025-06-11     
        reForge : done, a3, 2024-06-30, 2025-04-14
        Forge Classic : a4, 2024-08-11, 2025-06-17

    section Comfy UI
        ComfyUI : e1, 2023-01-17, 2025-06-17

In the graphs, the upper dots represent the release dates of image generation AI models, while the lower dots represent tools, with the left end indicating the release date and the right end showing the last update.

Tools in blue are still actively updated, while those in gray are no longer maintained.

August 2022: The Launch of Stable Diffusion 1

In August 2022, Stability AI released Stable Diffusion 1, marking the start of accessible local image generation.

However, running Stable Diffusion required writing Python code, which was a significant barrier for non-technical users.

Example code for running Stable Diffusion 1.5:

import torch
from diffusers import StableDiffusionPipeline

# Load the model
model_id = "runwayml/stable-diffusion-v1-5"
pipe = StableDiffusionPipeline.from_pretrained(model_id, torch_dtype=torch.float16)
pipe = pipe.to("cuda")  # For GPU usage

# Set the prompt
prompt = "A futuristic city at sunset, highly detailed, cinematic lighting"
negative_prompt = "blurry, low quality"  # Exclude unwanted elements

# Generate the image
image = pipe(
    prompt,
    negative_prompt=negative_prompt,
    num_inference_steps=50,  # Balance between quality and speed
    guidance_scale=7.5,     # Prompt adherence
).images[0]

# Save the image
image.save("generated_image.png")

The Rise of Stable Diffusion webUI!

To make Stable Diffusion more accessible, volunteer developers created a user-friendly interface that allowed users to run SD1 without coding, releasing it for free.

These tools, which ran Stable Diffusion through a web browser, became known as Stable Diffusion webUI.

The most popular among them was developed by Automatic1111, earning the nickname Stable Diffusion webUI A1111 and becoming synonymous with the tool itself.

Why A1111 Stands Out

Stable Diffusion webUI A1111 is intuitive and easy for beginners to pick up quickly. It also introduced some standout features:

Negative Prompt

A1111 leveraged Stable Diffusion’s unconditioning feature to implement Negative Prompt, allowing users to specify what they don’t want in their images.

This feature made image generation more stable and convenient, as users could exclude unwanted elements, significantly improving usability.

Custom Prompt Weighting

A1111 also introduced custom prompt weighting, reducing the likelihood of image generation failures even with complex prompts.

Today, generating images from almost any prompt with minimal failures is possible, thanks to the contributions of developers like Automatic1111.

July 2023: Stable Diffusion XL Arrives

In July 2023, Stable Diffusion XL (SDXL) was released, offering significant performance improvements over Stable Diffusion 1.

Key Features of SDXL:

• Training Resolution: 1024x1024 (compared to 512x512 for SD 1.5)
• Dual Text Encoders for enhanced text processing

SDXL’s Larger Footprint

However, SDXL’s model size was over three times larger than SD 1.5.

The larger model size increased VRAM usage, making it critical to optimize VRAM efficiency for SDXL and future models.

Stable Diffusion webUI Forge: Optimizing VRAM Usage

gantt
    title AI Image Generation Tools
    dateFormat YYYY-MM-DD
    tickInterval 6month

    section AI Models

        Stable Diffusion 1 : milestone, m1, 2022-08-22,
        Stable Diffusion XL : milestone, m2, 2023-07-26,
        Stable Diffusion 3 : milestone, m3, 2024-06-12,
        Flux.1 : milestone, m4, 2024-08-01,
        HiDream : milestone, m5, 2025-04-06,

    section Stable Diffusion<br>webUI
        A1111 : done, a1, 2022-08-22, 2024-07-27
        Forge : a2, 2024-01-14, 2025-06-11     
        reForge : done, a3, 2024-06-30, 2025-04-14
        Forge Classic : a4, 2024-08-11, 2025-06-17

    section Comfy UI
        ComfyUI : e1, 2023-01-17, 2025-06-17

In January 2024, Stable Diffusion webUI Forge, a fork of A1111, was released.

It retained A1111’s ease of use while adopting lightweight processing inspired by ComfyUI, particularly through Tiled VAE, which significantly improved generation speeds on mid-range GPUs by optimizing VRAM usage.

Forge Pursues Cutting-Edge Features

In July 2024, Forge announced it would prioritize new features over backward compatibility with A1111, resulting in about 30% of A1111’s extensions becoming unusable after upgrading to Gradio version 4.

However, when the next-generation Flux.1 model was released in August 2024, Forge quickly supported it, making it the only Stable Diffusion webUI option for Flux.1.

reForge Prioritizes Compatibility

gantt
    title AI Image Generation Tools
    dateFormat YYYY-MM-DD
    tickInterval 6month

    section AI Models

        Stable Diffusion 1 : milestone, m1, 2022-08-22,
        Stable Diffusion XL : milestone, m2, 2023-07-26,
        Stable Diffusion 3 : milestone, m3, 2024-06-12,
        Flux.1 : milestone, m4, 2024-08-01,
        HiDream : milestone, m5, 2025-04-06,

    section Stable Diffusion<br>webUI
        A1111 : done, a1, 2022-08-22, 2024-07-27
        Forge : a2, 2024-01-14, 2025-06-11     
        reForge : done, a3, 2024-06-30, 2025-04-14
        Forge Classic : a4, 2024-08-11, 2025-06-17

    section Comfy UI
        ComfyUI : e1, 2023-01-17, 2025-06-17

In July 2024, the original Stable Diffusion webUI A1111 quietly ceased updates. As Forge moved away from A1111 compatibility, many users were left in a bind.

That same month, Stable Diffusion webUI reForge, a fork of Forge, emerged to maintain compatibility with A1111’s extensions, prompting many A1111 users to switch.

reForge Supports v-pred

In December 2024, reForge added support for SDXL’s v-prediction anime models, solidifying its position as the go-to webUI for generating anime-style images with SDXL.

April 2025: reForge Development Ends

Despite active development and new features, reForge’s developers announced the project’s end in April 2025, citing time constraints.

Since most image generation AI tools are free, developers often face heavy demands with little tangible reward, highlighting the challenge of sustaining open-source projects as user bases grow.

Forge Classic Keeps Going

In July 2024, alongside reForge, Stable Diffusion webUI Forge Classic emerged, maintaining compatibility with A1111.

While not as widely adopted as reForge, Forge Classic supports v-pred models and is recommended by reForge’s developers as a successor tool, positioning it as a potential future standard.

ComfyUI: A Different Approach

Unlike Stable Diffusion webUI, ComfyUI takes a unique approach, functioning as a node-based UI that resembles a visual programming tool for designing AI workflows in a browser.

ComfyUI is lightweight, efficient with VRAM, and highly extensible, allowing anyone to create and integrate custom nodes.

ComfyUI Embraces Sponsorship

Unlike Stable Diffusion webUI, ComfyUI operates as a company, ComfyOrg, and accepts sponsorship.

With over $16.2 million in funding, ComfyUI is committed to ongoing open-source development, ensuring stability for long-term growth.

Other Image Generation AI Tools

Here’s a quick look at other tools beyond Stable Diffusion webUI and ComfyUI.

gantt
    title AI Image Generation Tools
    dateFormat YYYY-MM-DD
    tickInterval 6month

    section AI Models

        Stable Diffusion 1 : milestone, m1, 2022-08-22,
        Stable Diffusion XL : milestone, m2, 2023-07-26,
        Stable Diffusion 3 : milestone, m3, 2024-06-12,
        Flux.1 : milestone, m4, 2024-08-01,
        HiDream : milestone, m5, 2025-04-06,

    section Stable Diffusion<br>webUI
        A1111 : done, a1, 2022-08-22, 2024-07-27
        Forge : a2, 2024-01-14, 2025-06-11     
        reForge : done, a3, 2024-06-30, 2025-04-14
        Forge Classic : a4, 2024-08-11, 2025-06-17
        SD Next : a5, 2022-12-24, 2025-06-17
       
    section Fooocus    
        Fooocus : done, b1, 2023-08-09, 2025-01-24

    section Invoke AI
        Invoke AI : d1, 2022-08-17, 2025-06-17

    section Comfy UI
        ComfyUI : e1, 2023-01-17, 2025-06-17

    section Swarm UI
        Swarm UI: c1, 2023-05-12, 2025-06-17

Fooocus: The Simplest Image Generation Tool

Fooocus streamlined Stable Diffusion webUI’s features for ease of use, gaining popularity before its development ended.

SD Next: A Stylish A1111 Fork for Intel GPUs

SD Next, a fork of A1111, is designed for Intel GPUs and features a sleek, modern UI.

Invoke AI: Another Node-Based UI

Invoke AI is a professional-grade, node-based tool similar to ComfyUI, though their workflows are not compatible.

SwarmUI: Optimized for Multi-GPU Environments

SwarmUI is tailored for multi-GPU setups, like cloud environments, and supports both ComfyUI and A1111 functionalities.

So, Which Should You Choose?

Recommendation: ComfyUI

For those starting out, ComfyUI is the best choice due to its ongoing development and scalability.

EasyReforge: One-Click Setup for reForge

However, ComfyUI’s node-based interface can feel complex at first. For a simpler start, try Stable Diffusion webUI reForge with the EasyReforge one-click installer.

Conclusion: All Are Powerful Image Generation Tools

• A1111 laid the foundation for image generation AI tools
• Forge, reForge, and Forge Classic each offer unique strengths
• ComfyUI excels in extensibility

Each tool has its own origin story and distinct features, while also borrowing the best ideas from one another, as seen in how Forge was inspired by ComfyUI.

I’ve noticed comments in ComfyUI’s code where the developers mention drawing inspiration from A1111’s implementation.

In this vibrant open-source era, with developers worldwide contributing, I’m excited to keep exploring image generation.

Thanks for reading to the end!