Updated: September 3, 2026 · Docs · Clothoff AI Editorial Team
What is FLUX?
Black Forest Labs' image model family: open weights for developers, a non-commercial license on the larger checkpoints, and documented CSAM and NSFW risk mitigation.
FLUX is a family of text-to-image and image-editing models developed by Black Forest Labs, a German company started in 2024 by former Stable Diffusion researchers, with FLUX.1 released in 2024, the 32B FLUX.2 [dev] on Nov 25, 2025 and FLUX.2 [klein] on Jan 15, 2026. Weights are gated on Hugging Face under an acceptable use policy and a non-commercial license.
| Version | Date | Developer | License / Access | Filters |
|---|---|---|---|---|
| FLUX.1 [dev], [schnell], [pro] | 2024 (day not restated on the pages read) | Black Forest Labs | [schnell] Apache 2.0; [dev] non-commercial license; [pro] API only | API filters; dev weights gated with AUP |
| FLUX.2 [dev] (32B) | Nov 25, 2025 | Black Forest Labs | FLUX Non-Commercial License; outputs usable commercially per license text; weights gated | Model card documents CSAM and NSFW risk evaluation and training-data filtering |
| FLUX.2 [klein] 4B and 9B | Jan 15, 2026 | Black Forest Labs | 4B Apache 2.0; 9B FLUX Non-Commercial License | Same mitigations |
| FLUX.2 [pro], [flex], [max] | 2025 (API line; days not restated) | Black Forest Labs | API only via bfl.ai and partners | Provider-side moderation |
Black Forest Labs renamed the FLUX [dev] Non-Commercial License to FLUX Non-Commercial License in January 2026 without changing its terms.
Which FLUX versions exist and how are they licensed?
FLUX.1 launched in 2024 in three variants: [schnell] under Apache 2.0, [dev] under a non-commercial license and [pro] as API only. FLUX.2 followed on Nov 25, 2025 with a 32-billion-parameter [dev] checkpoint, and FLUX.2 [klein] on Jan 15, 2026 added 4B and 9B models for consumer hardware.
The license split is deliberate: the 4B [klein] model is Apache 2.0, while the 9B [klein] and the 32B [dev] fall under the FLUX Non-Commercial License. Black Forest Labs states that generated outputs may be used commercially even under that license, while the weights themselves may not be sold or served commercially.
“The "FLUX [dev] Non-Commercial License" has been renamed to "FLUX Non-Commercial License" and will apply to the 9B Klein models. No material changes have been made to the license.”
— Black Forest Labs blog, FLUX.2 [klein], accessed Sep 3, 2026
Does FLUX allow NSFW output?
The FLUX.2 [dev] model card states that Black Forest Labs evaluated CSAM and NSFW risks, filtered training data and applies additional mitigations, and the weights are gated behind an acceptable use policy that every downloader accepts. There is, however, no runtime classifier inside the open weights.
In practice a self-hosted FLUX model produces whatever the operator allows, and the ecosystem of fine-tunes and LoRA adapters includes explicit content. That does not change the legal position: an intimate image of a real, identifiable person without consent is unlawful whatever the base model, and breaches the FLUX acceptable use policy.
How is FLUX used in tools we review?
No tool in our rankings names FLUX publicly, but FLUX and Stable Diffusion are the two open image families that self-hosted services realistically choose from, so one of them likely sits behind most image generators until a vendor says otherwise. Our scoring does not depend on the guess.
For the image services we tested see the Ainudez review and the Pornworks review, and the generators hub for the full list. Inpainting and image-to-image, the two modes FLUX supports well, are the modes those tools expose.
Why does the non-commercial license matter to readers?
A service that serves the 32B FLUX.2 [dev] or 9B [klein] weights to paying customers needs a commercial license from Black Forest Labs; one using the 4B [klein] or FLUX.1 [schnell] does not. Readers cannot verify which weights a vendor runs, one more reason our reviews rate observable behavior.
The Stable Diffusion, inpainting and LoRA entries explain the neighboring concepts; the img2img entry covers the image-guided mode FLUX.2 added natively.
Consent note: tools in our rankings are documented for use only with photos of yourself or consenting adults 18+. See Responsible AI; if an image of you was misused, report NCII.
Sources
- Hugging Face — black-forest-labs/FLUX.2-dev model card — Nov 25, 2025; risk mitigation statements, accessed Sep 3, 2026.
- GitHub — black-forest-labs/flux2 — inference code, accessed Sep 3, 2026.
- Black Forest Labs — licensing — FLUX Non-Commercial License terms, accessed Sep 3, 2026.
- Black Forest Labs blog — FLUX.2 [klein] — Jan 15, 2026; license rename, accessed Sep 3, 2026.
- Black Forest Labs — FLUX.2 [klein] model page — 4B and 9B variants, accessed Sep 3, 2026.
Reference entry by the Clothoff AI Editorial Team; not legal advice. The access date marks the last verification.
Frequently asked questions about FLUX
Is FLUX open source?
Partly. FLUX.1 [schnell] and the 4B FLUX.2 [klein] are Apache 2.0, which is open source. FLUX.1 [dev], the 32B FLUX.2 [dev] and the 9B [klein] ship under the FLUX Non-Commercial License, and the [pro] models are API only. Black Forest Labs describes the family as open weights rather than open source.
When were FLUX.2 [dev] and [klein] released?
Black Forest Labs published the 32-billion-parameter FLUX.2 [dev] on Nov 25, 2025 and the FLUX.2 [klein] models in 4B and 9B sizes on Jan 15, 2026, according to the Hugging Face model card and the company blog read on Sep 3, 2026. FLUX.1 appeared in 2024; the pages read do not restate its day.
Does FLUX include a safety filter?
Not at runtime. The FLUX.2 [dev] model card documents CSAM and NSFW risk evaluation, training-data filtering and gated access under an acceptable use policy, but the open weights carry no classifier. The API models at bfl.ai apply provider-side moderation that self-hosted copies do not.
Can FLUX outputs be used commercially?
Yes, according to Black Forest Labs. Even under the FLUX Non-Commercial License, generated images may be used commercially; the restriction applies to hosting, selling or serving the weights themselves. Apache-licensed variants have no such limit. The license text on bfl.ai governs and should be read directly.
Is FLUX related to Stable Diffusion?
Institutionally, yes. Black Forest Labs was started in 2024 by researchers who previously worked on Stable Diffusion, and FLUX competes in the same open image model space. Technically FLUX is a separate architecture and weight family, not a Stable Diffusion checkpoint, and the two are not interchangeable.
Do the tools we review run on FLUX?
No reviewed tool names FLUX publicly, although FLUX and Stable Diffusion are the realistic open choices for self-hosted image services. Our rankings score tested behavior, mainly upload handling, retention, deletion and moderation, so the backbone guess does not change a tool's position.