The best data validation libraries, according to hackers
5 data validation libraries recommended in Hacker News comments over the past year, ranked by how many separate people recommend each one.
All data validation libraries
- PydanticPython library that validates data against type-annotated models, popular with FastAPI and AI output. Critics call it slow, heavy and prone to breaking changes.62recommend
- ZodPopular TypeScript schema library that validates untrusted data at boundaries and infers static types. Critics cite added dependency weight, inferred-type quirks, and the reported 4.6.6 malware compromise.58recommend
- clojure.specBuilt into Clojure, spec lets people express structural guarantees more expressively than an ordinary type system. Critics say it mostly retrofits static typing onto a dynamic language.18recommend
- MalliA Clojure library for runtime data validation and schema-based example generation; commenters prefer it to ordinary type systems for rigidity.15recommend
- Guardrails AIDevelopers recommend it for forcing AI agents to pass tests and build checks, and for being simpler with less code. It is free software.5recommend