Black Forest Labs is the team behind Stable Diffusion—and when some of that team split off to build something new, they created the Flux model family. Flux 1 Schnell ("schnell" is German for "fast") launched in 2024 as the speed-focused option. Flux 2 Dev followed in January 2025 with an upgraded architecture that trades speed for quality.
These two models represent a fundamental trade-off in AI image generation: how much quality are you willing to sacrifice for faster results? Flux 1 Schnell generates images in roughly one second, making it practical for real-time applications and rapid iteration. Flux 2 Dev takes about 2-3 seconds but produces noticeably better detail, prompt adherence, and overall coherence.
The cost difference reflects this gap. Flux 2 Dev is roughly 3-4× more expensive than Schnell for typical image sizes. For high-volume workflows, that difference adds up quickly.
One significant feature difference: Flux 2 Dev supports image-to-image generation, letting you use a source image as a starting point for modifications. Flux 1 Schnell is text-to-image only—if you need to iterate on an existing image, you'll need to use a different model.
Note: Both models are available through ImageGPT's quality routes. Flux 1 Schnell appears in "quality/fast" routes, while Flux 2 Dev is the backbone of "quality/balanced" routes.