Open-source alternatives to Rack

Elysia is a high-performance TypeScript web framework designed for building type-safe backend services. It provides a modular, plugin-based architecture that allows developers to compose server logic, middleware, and validation schemas into scalable application instances. By leveraging native web standards, the framework ensures portability across diverse JavaScript runtimes, including Node.js, Deno, and various edge computing environments. The framework distinguishes itself through its focus on end-to-end type safety, automatically synchronizing request and response definitions between the s

Wretch is a chainable HTTP client library and Fetch API wrapper designed to simplify network request configuration, response parsing, and error handling. It functions as a network request manager and middleware framework for managing the end-to-end lifecycle of HTTP calls. The project is distinguished by a fluent interface for request configuration and a modular extension system. It utilizes a programmable response resolver to automate parsing and a plugin-based architecture to add new capabilities to request and response objects. The library covers a broad range of operational capabilities,

go-restful is a framework for building RESTful web services in Go. It functions as a toolkit for managing API endpoints, providing a request router that maps incoming HTTP requests to handler functions using path parameters and custom URL patterns. The framework includes a data conversion layer that transforms Go structures into JSON or XML formats for request and response bodies. It also provides a system for organizing related web services into containers to manage endpoint prefixing and shared configuration. The project covers request lifecycle management through middleware filters for va

req is a chainable HTTP client library for Go designed to simplify request configuration and automatic response decoding into structures. It provides a fluent-interface request builder that allows developers to incrementally define request properties and encapsulate HTTP logic into reusable API SDKs. The project distinguishes itself with a TLS fingerprint emulator that mimics browser network signatures to bypass bot detection and crawler filters. It also includes a concurrent file downloader that increases transfer speeds by fetching large remote files in parallel segments. The library cover

Pollyjs is an HTTP mocking and recording library designed to capture and replay network interactions to create deterministic tests. It functions as a request interceptor and stubbing framework that records real API responses into files, ensuring consistent test results across different environments without relying on live network servers. The tool utilizes pluggable network adapters to support various environments and employs a state-based mode switching system to toggle between recording, replaying, and stubbing behaviors. It uses pattern-based request matching and persistent interaction sto

This is a minimal WebSocket library for Go designed for bidirectional real-time communication. It serves as a network protocol implementation for managing handshakes, frame masking, and control signals to enable the exchange of text and binary messages over persistent connections. The library distinguishes itself by providing a connectivity layer that wraps browser WebSocket APIs for applications compiled to WebAssembly. It also functions as data compression middleware, utilizing deflate compression to reduce bandwidth usage for transmitted messages. The project covers a broad range of netwo

Beast is a C++ library for implementing low-level HTTP and WebSocket clients and servers. It functions as an asynchronous networking framework designed to compose non-blocking I/O operations and layered stream stacks for managing concurrent network traffic, specifically utilizing the Boost.Asio asynchronous model. The library provides a comprehensive implementation of the HTTP/1.1 and WebSocket protocols. For HTTP, it includes primitives for parsing and serializing messages with support for chunked transfer encoding, incremental body reading, and request pipelining. Its WebSocket implementati

NanoHTTPD is a lightweight, embeddable HTTP server for Java applications. It allows developers to integrate web server capabilities directly into a Java project to handle incoming requests without requiring a standalone installation. The project provides specialized implementations for an HTTPS web server, a WebSocket server for bidirectional real-time communication, and a static file web server. These capabilities enable secure network traffic through SSL certificates and the delivery of local files with automatic MIME type detection. The server includes systems for request routing and hand

Starlette is an asynchronous web framework and toolkit for building high-performance web services based on the ASGI specification. It serves as a lightweight foundation for creating web applications with a focus on asynchronous request and response handling. The framework provides specialized toolkits for managing persistent bidirectional WebSocket communication and an asynchronous HTTP server toolkit for routing and middleware. It distinguishes itself by offering a non-blocking background task queue that executes functions after a response has been sent to the client. The project covers a b

Typhoeus is a Ruby wrapper for libcurl that functions as a session-based HTTP client. It provides an interface for making both synchronous and asynchronous network requests. The project acts as a parallel request manager, using a managed queue to execute multiple network requests concurrently. It further distinguishes itself as a mocking tool for stubbing requests with predefined responses and as a caching layer that stores responses to avoid redundant network calls. The library covers a broad range of capabilities including session cookie management, response body streaming for large files,

Armeria is a Netty-based microservice framework used for building high-performance asynchronous services. It functions as a multi-protocol RPC server capable of exposing gRPC, Thrift, and REST services on a single unified port. The project is distinguished by its ability to run diverse communication protocols simultaneously and its integrated RPC debugging web console, which allows for the discovery and invocation of remote procedure calls via JSON. It also includes a gRPC to JSON transcoder to enable web client compatibility with Protobuf services. The framework provides a comprehensive sui

Fasthttp is a high-performance networking framework for Go, designed to maximize throughput and minimize memory overhead in demanding web applications. It functions as a specialized HTTP server and client library that prioritizes efficient resource management, allowing developers to build scalable services capable of handling massive concurrent traffic with minimal garbage collection pressure. The library distinguishes itself through a focus on zero-allocation processing and low-level optimization. It achieves this by recycling temporary request and response objects through managed pools and

Rueidis is a high-performance Redis client library for Go that provides a type-safe and asynchronous interface for interacting with Redis servers. It includes a full implementation of the Redis serialization protocol and a dedicated connection manager to handle pooling, multiplexing, and automatic pipelining. The library is distinguished by its support for RDMA connectivity to reduce latency and CPU overhead. It features a distributed lock manager that implements majority-based locking and optimistic concurrency control, as well as client-side caching with invalidation signals to minimize net

Hono is a minimal JavaScript HTTP framework designed for building web servers across multiple runtimes, including Node.js, edge runtimes, and serverless platforms. It functions as a cross-runtime web server and a web standard API wrapper, normalizing various runtime request and response objects into standard Web API signatures. The project serves as an HTTP middleware orchestrator and request handler, utilizing a middleware-based request pipeline and hierarchical route mounting to create modular server structures. It distinguishes itself through a runtime-agnostic event wrapper that ensures c

Symfony Translation is a PHP library and framework component for internationalizing applications. It provides a complete system for managing message catalogs, handling locale-aware string translation, and formatting messages using ICU MessageFormat syntax to support pluralization, gender, and conditional selection. The component organizes translatable strings into named domains, supports key-based lookup that decouples source text from localized versions, and offers deferred rendering through translatable objects that store parameters and render only when output is needed. The library disting

Express-openapi-validator is an ExpressJS middleware that enforces API contract compliance by validating incoming requests and outgoing responses against OpenAPI 3.0 and 3.1 specifications. It acts as a gatekeeper for web services, ensuring that all traffic adheres to defined schemas before reaching application logic. The framework distinguishes itself by automating data integrity tasks, including the automatic coercion of request parameters and body content into typed objects. It provides comprehensive security enforcement by validating authentication and authorization headers against define

This project provides a server-side language runtime and a standardized Docker image for deploying applications across different operating systems. It functions as an execution environment for generating dynamic HTML, JSON, and XML content, while also serving as a command line interface for automation scripts and background jobs. The runtime is designed for extensibility through a C-based extension architecture, allowing the loading of custom modules for specialized functionality. It supports multiple server application interfaces, including a FastCGI web interface for high-performance commun

Falcon is a minimalist Python web API framework and high-performance microservices framework. It serves as a resource-oriented API toolkit designed for building RESTful APIs and data plane services that prioritize low overhead, reliability, and scale. The framework implements an ASGI web server interface to handle both synchronous and asynchronous HTTP requests and WebSockets. It features a dedicated HTTP middleware system for intercepting network traffic and executing shared processing logic across multiple API endpoints. Its capability surface covers resource-based routing, HTTP specificat

Faraday is an HTTP client library for Ruby that sends requests and processes responses through a middleware pipeline with pluggable adapters. Its core identity is built around a middleware-pipeline architecture where HTTP requests and responses flow through a chain of components that can modify, log, or transform data before reaching the backend, combined with an adapter-based backend abstraction that delegates HTTP execution to interchangeable backends like Net::HTTP or Typhoeus. The library distinguishes itself through a parallel-execution engine that dispatches multiple HTTP requests concu

MSW is a JavaScript API mocking library and integration testing tool designed to intercept network requests at the network level. It allows for the definition of mock data and status codes using routing syntax to simulate server responses without requiring changes to the application source code. The project utilizes a service worker to proxy API calls in the browser, providing a mechanism for isolated frontend development and testing. It employs platform-specific network adapters to maintain a consistent mocking interface across both browser and Node.js environments. The library covers a ran

Iron is a Rust web framework used for building concurrent web applications and APIs. It functions as a concurrent HTTP server and provides a stateless route dispatcher to map incoming URL paths and globs to specific handler functions. The project is centered around a middleware-based request pipeline, which allows the request-response cycle to be extended via plugins and modifiers. It utilizes a thread-safe state container to store shared application memory accessible across all concurrent handlers and middleware. The framework covers broad capability areas including dynamic API routing, sta

Mirage JS is a browser-based mock server and client-side API simulator designed for JavaScript application development. It functions as a mocking tool that intercepts network requests to simulate backend API behavior, allowing developers to build and test frontend interfaces without requiring live backend infrastructure. The tool provides a simulation layer that mimics REST endpoints to facilitate rapid prototyping of user flows and application logic. It enables the creation of fake server responses directly within the web browser to verify how an application handles various data scenarios an

The Swift OpenAPI Generator is a build-time tool that produces type-safe Swift client and server code directly from OpenAPI specification documents. By integrating with build systems through native plugins, it automates the creation of strongly-typed interfaces and protocol stubs that map network operations to native methods, ensuring that application code remains strictly consistent with defined data schemas. The project distinguishes itself through a protocol-oriented architecture that decouples business logic from specific transport implementations. It utilizes a pluggable transport layer

Axios is an isomorphic, promise-based HTTP client designed for making asynchronous network requests across different JavaScript execution environments, including the browser and Node.js. It functions as a JSON API client that serializes JavaScript objects into JSON and parses server responses into structured data. The project features a system for managing reusable client instances with shared configurations, such as base URLs and default settings. It includes a mechanism for intercepting outgoing requests and incoming responses globally, allowing data to be transformed before it reaches the

This repository is a collection of reference implementations and project scaffolds for the Koa web framework. It provides a set of boilerplates and examples for building Node.js web applications, including predefined project structures with database integrations and containerization. The project demonstrates the implementation of REST APIs and the use of HTTP middleware patterns for composing request handlers. It includes practical guides for designing structured endpoints and resource management patterns. The provided examples cover a range of capabilities including server-side rendering, r

This library provides a foundational set of tools for managing HTTP communication within PHP web applications. It focuses on the lifecycle of client-server interactions by parsing incoming request data into structured objects and facilitating the construction of protocol-compliant server responses. The architecture is built around immutable data structures that ensure state consistency throughout the application lifecycle. It incorporates lazy header parsing to reduce memory overhead and utilizes stream-based management for handling request and response payloads. By adhering to established co

Guzzle is a PHP HTTP client used for sending synchronous and asynchronous requests to web services. It serves as a concurrent HTTP request manager, an HTTP stream handler, and a middleware-based HTTP pipeline. The project is a PSR-7 compliant client, utilizing standardized PHP interfaces for requests, responses, and streams. The library differentiates itself through a customizable functional handler stack that allows for the interception and modification of the request and response lifecycle. It features an adapter-based transport system that enables swapping between network implementations,