Stable Diffusion is a family of open-weights image generation models from Stability AI. Unlike closed services, you can download the weights and run them on your own hardware, which is why it became the default base for a huge ecosystem of fine-tunes, LoRAs, ControlNets and local UIs.
The current release is Stable Diffusion 3.5, which ships in three variants: Large at 8.1B parameters, Large Turbo for fast few-step generation, and Medium at 2.5B for lighter machines. SD 3.5 is the most widely installed open image model by sheer install count, but it is no longer the quality leader among open weights — that position now belongs to Black Forest Labs' FLUX.2 as of 2026.
Capabilities cover text-to-image generation, prompt adherence and typography that improved over SDXL, and a broad toolchain for control and editing thanks to the open-model community. Related open models include SDXL Turbo, Stable Audio and Stable Fast 3D.
On pricing, self-hosting the open weights is free under the Stability AI Community License for individuals and organizations under $1M in annual revenue. Above that threshold an Enterprise License with custom pricing is required. Stability also offers a hosted route through the Developer Platform API (platform.stability.ai) with pay-per-credit billing: 1 credit is roughly $0.01, Stable Image Ultra runs about $0.08 per image and Stable Image Core about $0.03, with credit packs around $10 per 1,000 credits. A roughly $20/month membership tier has also been referenced by third parties.
The main limitations are practical. Running the larger models locally needs a capable GPU, results usually require prompt work and post-processing, and the revenue-gated license means larger companies cannot treat it as simply free. Quality at the top end now trails FLUX.2.
Stable Diffusion is the right choice if you want local control, an open pipeline you can fine-tune, and no per-image cost at small scale — and you are comfortable trading absolute peak quality for openness and flexibility.
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