YAML to Haskell Converter

YAML (YAML Ain't Markup Language) is used for Kubernetes manifests, Docker Compose, CI/CD pipelines, Helm charts, application config. Writing Haskell models from YAML by hand is repetitive and error-prone. This converter automates that step entirely — paste your YAML, get Haskell models instantly.

How to use this converter

1. Paste your YAML into the left editor panel
2. Click Generate
3. Copy the generated Haskell code from the right panel

No account. No upload. No tracking. Runs entirely in your browser.

Why automate YAML-to-Haskell conversion?

Writing Haskell data / newtype definitions by hand from YAML is:

• Tedious — especially for deeply nested or large YAML payloads
• Inconsistent — naming conventions drift when done manually across a team
• Fragile — when the YAML schema changes, hand-written models lag behind

Haskell's aeson library uses FromJSON/ToJSON type classes — this converter generates instances compatible with GHC's DeriveGeneric.

This converter handles all of that automatically, giving you idiomatic Haskell code that matches your YAML structure exactly.

Haskell and YAML: what you need to know

Haskell is a purely functional, lazy evaluation language, used in financial systems, compilers, and research. It uses data record types with Aeson for structured data — making it a natural fit for YAML-driven applications.

What the converter generates

The output consists of Haskell data types with Generic-derived Aeson instances. This is the idiomatic pattern for Haskell data models, compatible with popular Haskell serialization libraries.

A common gotcha

Haskell field naming conventions differ from JSON — aeson handles snake_case to camelCase automatically via defaultOptions.

YAML input characteristics

YAML is a superset of JSON and supports multi-line strings, block scalars, and complex nested structures. YAML is the de-facto standard for cloud-native configuration — Kubernetes, GitHub Actions, and Ansible all use YAML.

Common use cases

• Onboarding new team members by auto-generating the data layer
• Validating YAML contract compatibility with Haskell type definitions
• Generating Haskell models from financial modeling API responses
• Creating typed DTOs for compiler tooling
• Rapid prototyping with real YAML payloads
• Keeping Haskell structs in sync when YAML schemas evolve

Frequently asked questions

Can I use the output directly in a financial modeling project?

Yes. The generated Haskell code follows idiomatic patterns for financial modeling — you can copy it directly into your project.

Does this work for large YAML payloads?

Yes. The converter is optimized for large and deeply nested YAML structures, running entirely in the browser without page reloads or server round-trips.

Does this converter support YAML Ain't Markup Language namespaces and nested structures?

Yes. YAML supports anchors (&) and aliases (*) for reusable values — this converter resolves them before generating types. The parser handles deeply nested structures and generates matching nested Haskell data / newtype definitions.

How are optional fields handled in the Haskell output?

Fields that may be absent or null in your YAML are marked as optional in the generated Haskell code. Note: Haskell field naming conventions differ from JSON — aeson handles snake_case to camelCase automatically via defaultOptions.

Related tools on LangStop

• YAML Formatter & Validator — https://langstop.com/yaml-formatter
• YAML to TypeScript Converter — https://langstop.com/yaml-to-typescript
• YAML to Python Converter — https://langstop.com/yaml-to-python
• YAML to Go Converter — https://langstop.com/yaml-to-go
• YAML to JSON Schema — https://langstop.com/yaml-to-json-schema

If you work frequently with YAML and Haskell, bookmark this page to skip the manual model-writing step entirely.