Library / SDK
Guardrails & Structure
LMQL
1Programming 2language 3for 4constrained 5LLM 6prompting
the six Ws · specification
W1
Who
Maintained by the SRI Lab at ETH Zurich.
W2
What
A programming language that blends prompting with constraints, control flow, and typed outputs.
W3
Where
A Python-embedded library and runtime targeting local or API models.
W4
When
Reach for it when you want declarative, constraint-driven prompts with guaranteed shapes.
W5
Why
Expresses prompting logic and constraints as code for reliable generation.
W6
With
Works with Hugging Face Transformers, llama.cpp, and OpenAI models.
W7
Watch
Maintained by ETH Zurich's SRI Lab; open-source (Apache-2.0), self-hostable, no hosted service. Local backends run entirely on your infrastructure.