German AI startup Black Forest Labs has unveiled a new API that lets users customize their FLUX Pro AI image model to match specific brand styles using as few as five sample images.
The company's Finetuning API is meant to address a key limitation of current AI image generators: creating images that accurately match specific visual styles and brand identities. According to Black Forest Labs, the model maintains its flexibility after finetuning while incorporating what it learns from user-provided content into new image creations. The system can generate images at resolutions up to four megapixels.
Black Forest Labs designed the Finetuning API to work across its entire product range. The customized models integrate with both main offerings—FLUX.1 Pro and FLUX1.1 Pro Ultra—as well as specialized tools like FLUX.1 Fill for inpainting and FLUX.1 Depth for structural control.
German media company Burda Verlag uses the Flux Finetuning API to create customized versions of the image model for its various brands. For example, the company's creative teams can now generate images for the Lissy PONY children's brand in minutes, while preserving the brand's distinctive visual elements.
Technical details and availability
The API accepts common image formats including JPG, PNG, and WebP files. Users can upload between 1 and 20 training images, each with a maximum resolution of one megapixel. Black Forest Labs says optimal results require at least five high-quality images with clearly defined subjects.
Developers can adjust several training parameters, including the training mode (character, product, style, or general), number of training iterations (minimum 100, default 300), and learning rate. For output, developers can choose between quick training with faster inference or longer processing times that produce higher quality results.
Black Forest Labs has published specific recommendations for different use cases. For example, when training character models, the company suggests using images that show only one figure at a time. For style transfer work, testing higher finetuning strengths typically yields better results.
The FLUX Pro Finetuning API remains in beta testing and currently requires an API key for access. Black Forest Labs hasn't revealed pricing details or announced when the service will become widely available.