Open Source API Tools
Discover 179 open source API repositories from GitHub, each with an analysis of what it does, key features, use cases and alternatives. API projects here are most often combined with Self Hosted, Python and TypeScript. Last updated October 4, 2026.
179 repositories · updated October 4, 2026
orpc: Build End-to-End Type-Safe APIs
oRPC is a TypeScript toolkit for defining API contracts, implementing server procedures, and calling them with end-to-end type safety. It suits teams building TypeScript APIs that need OpenAPI compatibility and integrations with common frameworks and tools.
no-as-a-service: Return Random Rejection Reasons via an API
No-as-a-Service is a small JavaScript API that returns a random rejection reason as JSON. Use the hosted endpoint for playful “no” responses in apps and bots, or self-host it with Node.js and Express.
grpc-go: Build Go Services with gRPC
grpc-go is the Go implementation of gRPC, a high-performance RPC framework built around HTTP/2. Use it to define and implement RPC clients and servers in Go, especially for service-to-service communication.
java-sdk: Build MCP Clients and Servers in Java
The official Java SDK for building Model Context Protocol clients and servers. It provides transport and JSON integration options for Java applications that need to exchange requests, notifications, and streaming data with MCP services.
annas-mcp: Search and Download Documents with MCP or CLI
annas-mcp is a Go MCP server and command-line tool for searching books and articles in Anna's Archive and downloading selected documents. It suits MCP users and terminal workflows, with API access required for downloads.
supertokens-core: Build Authentication Into Your Applications
SuperTokens Core is a self-hostable authentication service that handles core login, user, and session operations for backend SDKs. It suits teams that want managed auth features while keeping user data in their own database and deployment.
ntfy: Send Push Notifications with HTTP Requests
ntfy is an HTTP-based publish-subscribe notification service for sending messages to phones and desktops. Publish from scripts with PUT or POST, use the hosted service, or run your own instance.
00: Self-Host an AWS SES Email Dashboard
00 is a self-hosted dashboard and API for sending email through AWS SES and tracking delivery events. It connects SES notifications through SNS and SQS so developers can search messages and monitor recipient-level status in one place.
kong: Route and Govern API, AI, and MCP Traffic
Kong Gateway is a cloud-native proxy for routing and managing API traffic, with features for LLM and MCP gateways. It suits teams that need a configurable gateway for services across Kubernetes or other infrastructure.
Damn-Vulnerable-RESTaurant-API-Game: Practice API Security
A deliberately insecure Python API for practicing vulnerability discovery, exploitation, and remediation. Developers, ethical hackers, and security engineers can run it locally with Docker as a controlled training environment.
docling-api: Convert Documents to Markdown Through an API
docling-api is a self-hostable FastAPI service that converts documents and images into Markdown using Docling. It suits teams that need synchronous or queued batch processing, with CPU and GPU deployment options.
carbon: Manage Manufacturing Planning and Production
Carbon combines ERP, MRP, MES and QMS in a shared Postgres-backed system for manufacturing teams. It covers planning, shop-floor execution, quality and traceability, with cloud and self-hosted deployment options.