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XML to Haskell Converter

XML is a attribute-rich, namespace-aware hierarchical document format — widely used for SOAP APIs, RSS/Atom feeds, Android layouts, enterprise data exchange. Converting it to strongly-typed Haskell structures eliminates runtime surprises and speeds up development. This tool does it in one click, entirely in your browser.

Generate Haskell data types with Aeson FromJSON / ToJSON instances for type-safe API parsing.

How to use this converter

  1. Paste your XML 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.

Example Haskell output

{-# LANGUAGE DeriveGeneric #-}
 
import GHC.Generics (Generic)
import Data.Aeson (FromJSON, ToJSON)
import Data.Text (Text)
 
data Address = Address
  { city :: Text
  , zip  :: Text
  } deriving (Show, Generic)
 
instance FromJSON Address
instance ToJSON Address
 
data User = User
  { userId  :: Int
  , name    :: Text
  , email   :: Maybe Text
  , address :: Address
  } deriving (Show, Generic)

Why automate XML-to-Haskell conversion?

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

  • Tedious — especially for deeply nested or large XML payloads
  • Inconsistent — naming conventions drift when done manually across a team
  • Fragile — when the XML 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 XML structure exactly.

Haskell and XML: 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 XML-driven applications.

What the converter generates

Output produces Haskell data declarations with deriving (Generic, Show) and Aeson FromJSON / ToJSON instances. Optional fields use Maybe and field names follow camelCase conventions.

A common gotcha

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

XML input characteristics

XML allows mixed content (text + child elements), namespaces, and CDATA sections — more expressive but more verbose than JSON. XML is the foundation of many enterprise integration standards including XSLT, XSD, and SOAP.

When should I use this converter?

Use this when building Haskell web services or scripts that consume external JSON/YAML data and need fully typed, Aeson-compatible data types.

Common use cases

  • Generating Aeson-compatible types for Servant or Yesod API handlers
  • Creating typed data structures for Haskell CLI tools parsing config files
  • Producing FromJSON instances for Haskell data pipeline scripts
  • Rapid prototyping with real XML payloads
  • Keeping Haskell structs in sync when XML schemas evolve
  • Onboarding new team members by auto-generating the data layer
  • Validating XML contract compatibility with Haskell type definitions
  • Generating Haskell models from financial modeling API responses
  • Creating typed DTOs for compiler tooling

Frequently asked questions

How are optional fields handled in the Haskell output?

Fields that may be absent or null in your XML 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.

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 XML payloads?

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

Does this converter support eXtensible Markup Language namespaces and nested structures?

Yes. XML supports both element content and attributes — this converter handles both when generating typed models. The parser handles deeply nested structures and generates matching nested Haskell data / newtype definitions.

Related tools on LangStop

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