If you have been following the latest developments in text-to-image models, you have probably heard about Flux - the revolutionize TextToImage model from Black Forest Labs that's been making waves in the AI art community.
Here, we are going to break down the three versions of Flux (Dev, Schnell, and Pro) to help you understand which one might be right for your needs. All the findings are community and our detailed testing.
Before diving into the comparison, let's quickly understand what makes Flux special. Released by Black Forest Labs, Flux is a text-to-image model trained with 12 billion parameters based on multimodal and parallel diffusion transformer block architecture.
You can install Flux models locally by following our step by step tutorial.
Table of Contents:
Model Types
There are three versions of Flux available:
1. Flux.1 Pro
- Access Method: API only through FalAI, Replicate, Freepik etc.
- License: Non Commercial
- Purpose: Raw version designed for testing
- Performance: Highest ELO test score (~1060) among all text-to-image models
- Installation: Not available for local download - accessible only via Black forest Labs API
2. Flux.1 Dev
- Access Method: Local download, Using API from FalAI, Replicate, Freepik etc.
- License: Non-commercial (personal, scientific, and non-commercial purposes)
- Hardware Requirements: High-end GPU with more than 12GB VRAM and 32GB system RAM
- Performance: Second highest ELO test score (~1050), very close to Pro version
- Key Feature: Guidance distilled model of Flux Pro - more powerful than the standard one
3. Flux.1 Schnell
- Access Method: Local download, Using API from FalAI, Replicate, Freepik etc.
- License: Apache2.0 (allows commercial use)
- Hardware Requirements: Works on GPU with 12GB VRAM or lower
- Key Feature: Capable of generating decent-quality images in only 1 to 4 steps
We will be comparing the Dev and Schnell model because we are discussing the models that can be downloaded and accessed either locally/remotely. So, we will be leaving the Pro variant due to its heavy restrictions by their owners.
1. Installation Options
Flux can be used on three major platforms:
(a) ComfyUI: Most flexible with all variants supported
(b) ForgeUI: Good support for optimized variants
(c) API (for Flux Pro): Through FalAI platform
(d) SwarmUI (newer support)
Automatic1111 support is currently unavailable.
2. Performance and Quality
Based on the testing described in the documentation:
- Flux Pro: Highest quality, perfect for commercial applications
- Flux Dev: Very close to Pro quality, excellent detailing, prompt adherence, and scene complexity
- Flux Schnell: Good quality with significantly faster generation times, may require multiple attempts for perfect results
3. Optimized Variants for Different Hardware
If you are running on lower-end hardware, several optimized variants are available:
For Flux Dev:
- Official release: High VRAM requirements (>12GB)
- GGUF Quantized versions: Lower VRAM consumption
- Comfyanonymous FP8-bit: For GPUs with lower VRAM (≤12GB)
- Kijai FP8-bit: Alternative for lower-end GPUs (some quality reduction)
- lllyasviel's optimized variants:
- flux1-dev-bnb-nf4 / flux1-dev-bnb-nf4-v2: For NVIDIA RTX 3000/4000 series (CUDA >11.7)
- Flux Dev FP8: For NVIDIA GTX 1000/2000 series cards
For Flux Schnell:
- Official release: Works on 12GB VRAM or lower
- GGUF Quantized versions: Even lower VRAM consumption
- Comfyanonymous FP8-bit: For very low VRAM systems
- SilverOxides' bnb NF4: For RTX 3000/4000 series GPUs
4. Real-World Performance Examples
We found interesting results elaborated below:
(a) Typography and Text Handling: Flux Dev showed excellent prompt adherence and typography rendering, outperforming Flux Schnell in complex text scenarios.
(b) Human Face Generation: Both models produces chins and plastic faces if you are familiar. To get the realism you need detailed prompting.
(c) Photography: Flux Dev produced the expected result on the first attempt. Flux Schnell requires sometimes multiple attempts to get a perfect result. Both models captures impressive details but it actually depends what you need.
(d) Realism: Schnell generates and struggles more than that of Dev variant.
(e) Human Fingers: Dev version creates more satisfied generation as compare to Schnell.
5. Suitable model Variant
Now, you might be confused which model variant is suitable for your use case.
- Go with Flux Pro: If you need the absolute best quality for testing projects and don't mind using an API
- Choose Flux Dev: If you have powerful hardware and need top-quality results for non-commercial use
- Opt for Flux Schnell: If you need faster generation times, have limited hardware, or require commercial licensing
6. Image Quality and Detail Level
Well, Flux Dev consistently produces higher quality images with better details, particularly notable in:
- Skin texture and realism: The skin realism looks way better in Flux Dev than the Schnell with Dev showing more natural skin tones, pores, and subtle variations
- Fine details: Dev captures more intricate textures, fabric details, and environmental elements
- Lighting effects: More sophisticated handling of shadows, highlights, and reflections
Flux Schnell still produces impressive images, but side-by-side comparisons show Dev has the edge in overall fidelity and realism.
7. Speed and Performance
This is where Flux Schnell truly shines and lives up to its name ("schnell" means "fast" in German):
- Flux Dev: Requires 20-50 steps for optimal results (typically 30-40 recommended)
- Flux Schnell: Can produce remarkable results in just 1-4 steps
Several users in the community debated whether increasing steps beyond 20 for Flux Dev makes any noticeable difference, with the consensus being that 20-30 steps provides the sweet targeted spot for quality versus time.
8. Hardware Requirements
The hardware differences are significant when you want optimized results:
Flux Dev:
- Ideal: >12GB VRAM with 32GB system RAM
- Can run on 12GB VRAM with optimized variants, but may encounter memory issues at higher resolutions
Flux Schnell:
- Designed to run on 12GB VRAM or less
- Can work on cards with as little as 8GB VRAM using optimized NF4/ quantized GGUF versions
9. Optimized Variants
The community has created several optimized variants to improve performance:
- Flux Valhalla: A community-optimized version of Flux Schnell that reportedly offers the fastest Flux Schnell quality with speed improvements.
- OpenFlux: An open-source recreation showing promising results compared to official models
- GGUF Quantized versions: Lower VRAM consumption variants for both models
- FP8-bit versions: For running on older/lower-end GPUs
10. Prompt Following Ability
Flux Dev shows superior prompt adherence, especially with complex or specific requests:
- Text rendering: Dev handles text in images much more accurately
- Specific details: Better at including all elements mentioned in prompts
- Complex concepts: More reliable with abstract or unusual concepts
By understanding different concepts its been concluded that Dev has a clear advantage for precise prompts.
11. Optimal Settings
For Flux Dev:
- Sampling Method: Euler
- Steps: 20-30 (diminishing returns beyond 30 according to most users)
- CFG: 3.5
- Resolution: 1024×1024 optimal (some users also reported good results up to 1536×1536)
For Flux Schnell:
- Sampling Method: Euler
- Steps: 1-4 (surprisingly good results even at 1 step)
- CFG: 1-2
- Resolution: 1024×1024 (smaller resolutions still produce good results)
12. Resolution Handling
A comparative analysis looked at different image resolutions with both models:
- Both models handle 1024×1024 extremely well
- Flux Dev maintains better quality at higher resolutions (1536×1536)
- Schnell shows more degradation at higher resolutions but works impressively well at lower resolutions
13. Use Cases
Choose Flux Dev when:
- Image quality is your top priority
- You have higher-end hardware
- You need superior prompt following for complex concepts
- You are creating non-commercial work for testing only
- You need photorealistic human faces and skin textures
- You have time for longer generation cycles
Choose Flux Schnell when:
- Speed is essential
- You have limited hardware resources
- You need commercial usage rights
- You are doing quick iterations or concepts
- You are fine with slightly less precise prompt following
- Your prompts are relatively straightforward
Conclusion
After extensive testing, it's clear that Flux represents a significant leap forward in text-to-image generation. While Flux Dev offers the highest quality for local installation, Flux Schnell provides an impressive balance of speed and quality, especially for users with more limited hardware.
The availability of optimized variants means nearly anyone can run some version of Flux, regardless of their hardware constraints. As the community continues to develop additional tools and optimizations, we can expect even better performance and accessibility in the future.
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