Why I stopped copy-pasting JSON into online converters and built TypeMorph
Every developer has done it. You grab a JSON response from an API, paste it into some random online tool, and get a TypeScript interface back. Fast, convenient — and potentially a huge security mistake.
I did this for years before I realized what I was actually doing: sending production API responses, internal data models, and sometimes customer data to servers I knew nothing about.
So I built TypeMorph (https://typemorph.dev) — a schema conversion tool that runs 100% in your browser. No servers. No uploads. Your data never leaves your machine.
The problem with online converters
Most "free" online converters are not actually free. You're paying with your data.
When you paste a JSON payload into a third-party tool:
- That payload hits their servers
- It may be logged, stored, or analyzed
- If it contains PII or proprietary business logic, you just leaked it
For personal projects this might be fine. But for a startup or enterprise team? One slip and you've violated your own data handling policies.
What TypeMorph does differently
TypeMorph uses a single AST pipeline that runs entirely in your browser:
JSON / YAML / OpenAPI / JSON Schema
└─► inferSchema() → Schema AST
└─► generators → 160+ output formats
Everything is client-side. There is no backend. The conversion happens in your tab and stays there.
160+ output formats
TypeMorph doesn't just do TypeScript. Paste one JSON object and get:
- Validation schemas: Zod, Yup, Valibot, ArkType, Joi
- Languages: Go, Rust, Python (Pydantic), Java, Kotlin, Swift, C#, Dart
- Databases: Prisma, Drizzle, Kysely, MySQL, PostgreSQL, MongoDB
- API: OpenAPI, Postman, Protobuf, GraphQL
- Frontend: React Props, Vue Props, Pinia, Redux Slice
And it's not dumb code generation. The Zod generator applies semantic validators automatically:
// Input JSON: { "email": "user@example.com", "age": 28, "score": 94 }
// TypeMorph output:
export const rootSchema = z.object({
email: z.string().email(), // detected from field name
age: z.number().int().min(0).max(150), // semantic range
score: z.number().min(0).max(100), // semantic range
});
Schema Quality Score
TypeMorph grades your schema A–F and tells you why:
- Fields typed as any
- Missing format constraints (uuid, email, datetime…)
- Mixed naming conventions (camelCase vs snake_case)
- Overly deep nesting
It's like a linter for your data model.
Breaking Change Detector
Paste two versions of a schema and TypeMorph tells you exactly what broke:
0% compatible · 7 breaking · 1 info
❌ id REMOVED — Required field 'id' was removed
❌ name REMOVED — Required field 'name' was removed
⚠️ user_id ADDED — New required field. Existing payloads will be invalid
This alone has saved me from shipping breaking API changes more than once.
VS Code Extension
Last week I shipped a VS Code extension so you don't even need to open a browser.
Ctrl+Shift+T on any JSON file → pick a format → output appears in a side panel.
Install it from the VS Code Marketplace (https://marketplace.visualstudio.com/items?itemName=TypeMorph.typemorph-vscode).
CLI for CI pipelines
npm install -g typemorph-cli
typemorph zod schema.json # convert to Zod
typemorph quality schema.json # schema quality score
typemorph diff v1.json v2.json # breaking change detection
Try it
- Web: https://typemorph.dev
- VS Code: Marketplace (https://marketplace.visualstudio.com/items?itemName=TypeMorph.typemorph-vscode)
- CLI: npm install -g typemorph-cli
If you've ever pasted company data into a random online tool and immediately felt uneasy about it — TypeMorph is for you.
What output formats do you wish existed? Drop them in the comments.
ents.