TypeSpec

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What TypeSpec is

TypeSpec is an open-source language for defining API shapes and data models, then generating schemas, API specifications, code, and documentation. Inspired by TypeScript, it lets teams describe an API in a lightweight form and use shared models across outputs. Its standard library supports OpenAPI 3.0, JSON Schema 2020-12, and Protobuf. OpenAPI output can feed tools for API gateways, code generation, and validation, while JSON Schema can validate data against those models. TypeSpec also supports authentication modeling through its HTTP library, with options including HTTP authentication, API keys, OAuth2, and OpenID Connect.

Developers can add custom decorators or build emitters. Editor support is available for Visual Studio Code and Visual Studio; the VS Code extension includes completion, diagnostics, formatting, refactoring, and API documentation preview. The CLI is available through npm for Node.js, with a standalone executable marked experimental, and an online playground is available. TypeSpec is free, with a listed price of $0. Its emitter framework is experimental, and client emitters for JavaScript, Python, Java, and C# are in preview and subject to change.

Who it suits

TypeSpec suits developers designing API contracts and data models who want to generate standard schemas or specifications. It also fits teams using VS Code or Visual Studio, or trying the language in a browser playground.

What it does well

Free and open source.
Supports OpenAPI, JSON Schema, and Protobuf.
Models HTTP authentication schemes.
VS Code extension includes diagnostics and refactoring.
Browser playground available.

What to know first

Emitter framework is experimental.
Client emitters are in preview and may change.
Standalone executable is marked experimental.
VS Code extension sends usage data to Microsoft.

Limits

TypeSpec is free and open source. Its emitter framework is experimental, and the listed JavaScript, Python, Java, and C# client emitters are in preview and subject to change.

Plans

Plan	Billed and limits	Price
TypeSpec	Open-source project; TypeSpec CLI and online playground	Free

As typespec.io lists them, read 3 Oct 2026. The maker's own page has the final word.

Getting started

Open the TypeSpec website and try the linked browser playground.
Install the CLI through npm for Node.js, or use the experimental standalone executable.
Follow the installation instructions for macOS, Windows, or Linux.
Add the TypeSpec extension to Visual Studio Code or Visual Studio for editor support.

Verdict

TypeSpec combines API modeling with generation of several common schema and specification formats. Its emitter framework and client emitters are still experimental or in preview, so users should account for that status when choosing it.

Questions

How much does TypeSpec cost?

TypeSpec is listed as free. It is an open-source project, and no paid plan is listed.

Which output formats does TypeSpec support?

Its standard library supports OpenAPI 3.0, JSON Schema 2020-12, and Protobuf.

Which editors does it support?

TypeSpec provides language support for Visual Studio Code and Visual Studio. Its VS Code extension includes features such as IntelliSense, diagnostics, formatting, and API documentation preview.

Can TypeSpec model API authentication?

Yes. The HTTP library’s @useAuth decorator applies authentication schemes to services, namespaces, interfaces, or operations. Documented options include HTTP authentication, API keys, OAuth2, and OpenID Connect.

Can I use TypeSpec in a browser?

Yes. The official site links to an online TypeSpec Playground.

Is its code generation mature?

The emitter framework is experimental and under active development. Client emitters for JavaScript, Python, Java, and C# are in preview and subject to change.

Facts from TypeSpec's own pages

Authentication modeling: The HTTP library's @useAuth decorator supports applying authentication schemes to a service namespace, sub-namespace, interface, or operation. · typespec.io, 3 Oct 2026
Browser playground: The official site links to a TypeSpec Playground for trying TypeSpec in a browser. · typespec.io, 3 Oct 2026
Built-in formats: Its standard library supports OpenAPI 3.0, JSON Schema 2020-12, and Protocol Buffers (Protobuf). · typespec.io, 3 Oct 2026
Client generation: The client emitter guide lists JavaScript, Python, Java, and C# client emitters and says they are in preview and subject to change. · typespec.io, 3 Oct 2026
Data validation: The JSON Schema emitter can produce schemas from shared models for validating data. · typespec.io, 3 Oct 2026
Editor integrations: TypeSpec provides language support for VS Code and Visual Studio, including syntax highlighting and code completion. · typespec.io, 3 Oct 2026
Editor support: TypeSpec provides extensions for Visual Studio Code and Visual Studio. · typespec.io, 3 Oct 2026
Emitter status: The emitter framework is experimental and under active development, and the documentation says only TypeScript is well supported at the time of that page. · typespec.io, 3 Oct 2026
Extensibility: Developers can write custom emitters or add metadata with custom decorators. · typespec.io, 3 Oct 2026
Installation: The CLI is available as an npm package for Node.js or as a standalone executable marked experimental; installation instructions cover macOS, Windows, and Linux. · typespec.io, 3 Oct 2026
Integrations: The VS Code extension can import TypeSpec from existing OpenAPI 3 definitions and emit code from TypeSpec. · typespec.io, 3 Oct 2026
Language: TypeSpec is inspired by TypeScript and is described as a lightweight language for defining API shapes. · typespec.io, 3 Oct 2026
Maker: TypeSpec describes itself as a Microsoft-built, community-supported project. · typespec.io, 3 Oct 2026
Online access: The site provides an online playground for trying TypeSpec. · typespec.io, 3 Oct 2026
OpenAPI workflow: TypeSpec can generate OpenAPI specifications for use with tools for API gateways, code generation, and data validation. · typespec.io, 3 Oct 2026
Output formats: The standard library supports OpenAPI 3.0, JSON Schema 2020-12, and Protobuf. · typespec.io, 3 Oct 2026
Pricing: The official homepage and documentation pages reviewed present TypeSpec as an installable project and do not list paid plans or prices. · typespec.io, 3 Oct 2026
Publisher and support: TypeSpec is described as a Microsoft-built, community-supported project. · typespec.io, 3 Oct 2026
Purpose: TypeSpec is a language for designing APIs and data models, then generating schemas, API specifications, code, and documentation. · typespec.io, 3 Oct 2026
Supported auth schemes: Documented security scheme options include HTTP authentication, API keys, OAuth2, and OpenID Connect. · typespec.io, 3 Oct 2026
Telemetry: The VS Code extension collects usage data and sends it to Microsoft; the page says it respects the telemetry.telemetryLevel setting. · typespec.io, 3 Oct 2026
Telemetry privacy: The VS Code extension documentation says unknown customer emitters are masked and compiler location telemetry does not store the actual compiler path. · typespec.io, 3 Oct 2026
VS Code features: The VS Code extension provides IntelliSense, syntax highlighting, completion, formatting, diagnostics, quick fixes, refactoring, and API documentation preview. · typespec.io, 3 Oct 2026