JSON to Haskell Generator

Definition

This tool converts JSON into Haskell directly in your browser—no upload, no account. Paste or load your JSON on one side and copy accurate Haskell from the other, with structure preserved for APIs, configs, and data pipelines. On JSON Nova, conversion stays private on your device with Monaco editing and support for large payloads.

Generate Haskell from JSON in the browser. Private, no upload. Validate JSON first. For APIs, DTOs, and codegen. See also JSON to CSV, JSON Formatter, and JSON Validator.

Run everything in your browser with Monaco Editor on JSON Nova—100% client-side, no server uploads, large-file friendly. Install as a PWA for offline use.

Guide and tips

Developer guide

Short, practical notes—workflow, common mistakes, and pro tips—with links to related tools.

Convert JSON → Haskell

Generate Haskell from JSON in the browser. Private, no upload. Validate JSON first. For APIs, DTOs, and codegen.

All processing stays in your browser. Paste production-shaped samples without uploading secrets.

Workflow

Start with a small, representative sample. Confirm structure, then scale to full exports.

If the source is JSON, fix encoding and delimiters before converting—garbage in propagates to Haskell.

Related: JSON Formatter, JSON Validator.

Common mistakes

Assuming the converter will repair invalid source data. Clean the input first.

Pasting huge blobs without testing memory limits in the browser tab.

Skipping a round-trip check in your real pipeline (DB, API, or build step).

Treating converted output as trusted without schema or type checks downstream.

Pro tips

Version-control a golden sample and diff converter output in CI.

Related: JSON Formatter, JSON Validator.

Name fields consistently so future re-imports stay stable.

Quick reference

What is JSON to Haskell?

Generates **Haskell** types or models from **JSON** data in the browser. Useful for DTOs, API clients, and codegen from sample payloads. Pair with JSON Validator when your JSON is copied from logs.

Use cases

  • Bootstrap Haskell structs from a real API response or OpenAPI sample.
  • Prototype services without hand-typing large nested objects.
  • Share generated code in PRs for team review.

Common errors

  • Invalid JSON: unclosed tags or bad JSON—fix source before codegen.
  • Ambiguous arrays of mixed types—generated types may use union or any-style escapes.
  • Very deep nesting—some generators flatten or truncate; simplify test JSON if needed.

Best practices

Keep samples small but representative. Use JSON to TypeScript and JSON Validator first. Explore JSON to Zod for runtime schemas alongside Haskell types.

Performance and privacy

Performance

Leverage the power of Monaco Editor and Web Workers. Our toolkit is optimized for files up to 50MB, providing real-time transformations without lag.

Privacy

Your data stays local. Conversions and formatting run 100% in your browser—nothing is sent to our servers.

Frequently asked questions

FAQ

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How does it handle Type Safety?

It maps JSON fields to Haskell ADTs (Algebraic Data Types), ensuring absolute compile-time type safety for your data.

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Is it compatible with Serialization?

Yes, generated types are highly compatible with the popular Aeson library for GHC.Generics based JSON serialization.

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How is Null Safety handled?

Uses Haskell's native Maybe type for optional or nullable fields, ensuring exhaustive pattern matching at compile time.

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Does it support nested records?

Yes, nested JSON structures are converted into separate Haskell data types to maintain a clean and idiomatic functional design.

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Is it compatible with GHC 9+?

The generated code uses standard Haskell features compatible with all modern GHC versions, including the latest 9.x releases.

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Can I use records for all objects?

Yes, the generator uses record syntax by default, providing easy access to fields and better integration with Aeson's generic instances.

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Are there any dependencies?

You'll typically need the 'aeson' and 'text' libraries in your Cabal or Stack project to work with the generated data types.

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