Welcome to CUE!

CUE is an open-source data validation language with its roots in logic programming. It combines succinct yet clear syntax with powerful, flexible constraints that enable data, schema, and policy constraints to coexist seamlessly:

area:   length * width
area:   <100        // Must be less than 100.
width:  33.3 & >10  // Must be greater than 10.
length: 5 & !=width // Reject square areas.

$ cue vet example.cue
area: invalid value 166.5 (out of bound <100):
    ./example.cue:2:9
    ./example.cue:1:9

CUE supports and simplifies a wide variety of applications, such as data validation, configuration, querying, and code generation, with its underlying inference engine enabling data validation in code, and flexible generation pipelines.

How to use this documentation

Browse through the different documentation sections, or use the search box in the top-right corner of each page. Here’s what you’ll find in each section: