API Studio
A fully offline, privacy-first API client for VS Code, CLI, and Electron desktop. Test REST, GraphQL, WebSocket, and gRPC APIs without cloud accounts, telemetry, or network dependencies. Your data stays on your machine — always.
Key Highlights
Fully Offline
No cloud, no accounts, no telemetry. Works without internet.
No Account Required
Install and start testing immediately. Zero sign-up friction.
Git-Friendly
Plain JSON files in .openpost/ — commit and share with your team.
4 Protocols
HTTP/REST, GraphQL, WebSocket, and gRPC in one tool.
Mock + MCP Servers
Built-in mock servers with Swagger docs and AI-client MCP integration.
Encrypted Vault
AES-256-GCM encrypted secrets and certificates with auto-resolution.
15 Language Export
Generate ready-to-use code in cURL, Python, Go, Rust, Java, and more.
CLI Runner
Run collections from CI/CD pipelines via the openpost npm package.
What's Included
VS Code Extension
Full-featured API client embedded in your editor. Multi-tab interface, collections, environments, mock servers, and MCP integration.
Installation guide →CLI / npm Package
Run collections headlessly from CI/CD pipelines. Import, export, manage vault secrets, and serve mock servers from the terminal.
CLI documentation →Electron Desktop App
Standalone desktop application with the same powerful features — no VS Code required. Cross-platform for macOS, Windows, and Linux.
Coming soonFeature Overview
HTTP Client
All HTTP methods, query parameters with bidirectional URL sync, custom headers with autocomplete, multi-tab interface with session persistence, and HTTP/2 auto-negotiation.
GraphQL
CodeMirror 6 editor with schema-aware autocomplete and lint, introspection, SDL import, visual query builder, docs panel, multi-operation support, and graphql-transport-ws subscriptions.
WebSocket
Connect to ws:// and wss:// endpoints for real-time two-way communication. Message log with direction indicators, timestamps, and JSON pretty-printing.
gRPC
Unary and server-streaming calls with .proto file loading, service/method picker, metadata headers, auth injection, TLS certificates, and grpcurl code export.
Collections
Organize requests into collections with nested folders, drag-and-drop reordering, auth/script inheritance, collection runs, and Postman/OpenAPI import-export.
Authentication
Seven auth types — Basic, Bearer, API Key, OAuth 2.0, AWS SigV4, and Digest — all supporting {{variable}} placeholders and inheritance chains.
Testing
GUI-based test rules for no-code assertions, pre-request and test scripts in sandboxed JavaScript, and response variable extraction.
Mock Servers
Multi-instance mock servers with custom routes, request logging, auto-generated Swagger docs, and optional MCP tool exposure for AI clients.
MCP Servers
Built-in Management MCP server with 33 tools. Connect any AI client (Copilot, Cursor, Kiro, Claude Desktop) to manage your workspace via natural language.
Secret Vault
AES-256-GCM encrypted local vault for secrets and TLS certificates. Secret sets map vault entries to {{variable}} placeholders with automatic scrubbing from persisted data.
CLI
Headless collection runner for CI/CD pipelines. Import/export, vault management, and mock server hosting from the command line.
Code Export
Generate code in 15 languages: cURL, PowerShell, JavaScript, Python, Go, Java, C#, Ruby, PHP, Rust, Swift, and grpcurl. Auth and env vars auto-resolved.
Popular Pages
System Requirements
| Component | Requirement |
|---|---|
| VS Code Extension | VS Code 1.85.0 or later |
| CLI / npm package | Node.js 18 or later |
| Electron Desktop | macOS 12+, Windows 10+, or Linux (x64/arm64) |
| Network | None — fully offline (internet only needed to reach your APIs) |
Next Steps
New to API Studio? Start with the installation guide, then follow the quick start tutorial to send your first request in under a minute.