Open-source alternatives to Requestly

Mockoon is an HTTP API simulation platform and design tool used to create fake API endpoints that simulate server responses without a backend. It functions as an OpenAPI mock server tool and a JSON API mocking utility, allowing for the rapid iteration of API contracts and the generation of response templates. The project distinguishes itself through a combination of stateful mocking, using a local JSON database to simulate CRUD operations, and the ability to run as a headless API mock server via a command line interface. It supports real-time collaborative editing and AI-assisted prototyping

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

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

Quarkus is a Kubernetes-native Java framework designed for building high-performance, memory-efficient applications. It utilizes ahead-of-time native compilation to transform Java code into standalone, optimized binaries that eliminate the need for a virtual machine, enabling rapid startup and reduced memory consumption. By performing code augmentation during the build phase, it shifts heavy processing tasks away from runtime, ensuring that applications are optimized for cloud-native environments. The framework distinguishes itself through a unified approach to reactive and imperative program

rrweb is a DOM session recording library and serialization framework used to record and replay web sessions. It converts the state of a web page into a serializable JSON data structure and tracks mutations to reconstruct user interactions within a replay engine. The system distinguishes itself by using a sandboxed iframe for reconstruction to isolate replayed content, preventing script execution and form submissions. It ensures visual consistency through CSS inline-style flattening and provides sensitive data masking to prevent private information from being captured. The project covers a br

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

Tamperchrome is a browser-based API debugger and network interceptor designed for the real-time manipulation of HTTP traffic. It functions as a proxy alternative that allows for the capturing and modification of requests and responses directly within the browser environment. The tool enables API response mocking and the alteration of server data before it reaches the page. It provides capabilities for modifying outgoing request headers and bodies, as well as injecting content into response bodies to test client-side behavior. The project covers a broad surface of network debugging, including

Proxypin is a cross-platform HTTP and HTTPS proxy debugger designed to capture, inspect, and modify network traffic. It functions as a man-in-the-middle interceptor, allowing developers to analyze application data flows and validate network communication during development and testing. The tool distinguishes itself through its focus on mobile and remote device integration, utilizing QR-code-based configuration synchronization to simplify the setup of proxy settings and security certificates. It includes an event-driven scripting engine that enables programmatic manipulation of requests and re

Karate is a Gherkin API testing framework and JVM test orchestrator designed for API validation, workflow automation, and browser automation. It provides a unified environment for executing scriptable logic on the Java Virtual Machine with thread-safe concurrent processing. The project includes a built-in HTTP mock server to simulate backend API behavior by delivering dynamic responses to intercepted requests. It also features a visual regression testing tool that detects interface changes by comparing screenshots against baseline images using pixel-matching analysis. The system supports API

GoReplay is a network traffic recording and replay tool used to capture live HTTP and binary protocol requests. It functions as a traffic shadowing proxy that duplicates incoming network requests to test environments and a utility for recording traffic to local or cloud storage for later analysis and playback. The system is capable of processing non-textual data formats, such as Thrift and Protocol Buffers, allowing for the capture and replay of specialized application-to-application communication. The tool supports live traffic capture and asynchronous duplication to validate infrastructure

Altair is a graphical GraphQL API client, integrated development environment, and schema explorer. It functions as a debugging tool and collaboration platform for executing queries, mutations, and subscriptions against GraphQL servers. The project distinguishes itself by offering cloud-synced workspaces for organizing and sharing query collections among teams. It provides a flexible extensibility framework that allows the installation and execution of third-party plugins within isolated sandboxes. The platform covers a broad range of capabilities, including AI-assisted query writing, visual

Hetty is an HTTP intercepting proxy and web security research toolkit used to capture, inspect, and modify traffic between a browser and a server. It functions as an HTTP request editor for creating and replaying manual requests to test server behavior and as a project-based traffic logger that isolates network logs across different security research engagements. The tool provides a request-response interception loop that pauses outgoing requests and incoming responses in transit, allowing for manual editing or cancellation. It includes a manual request replay engine to construct and transmit

Rest-assured is a Java-based REST API testing framework and HTTP client library designed for automating web service tests. It provides a fluent domain-specific language and assertion library to send HTTP requests and validate response metadata, including status codes, headers, cookies, and bodies. The framework is distinguished by a method-chaining DSL that creates readable specifications for API interactions. It features a filter-based request interception pipeline, object-mapping serialization for converting Java objects to JSON or XML, and a path-based parsing system to isolate specific fi

w3af is a web penetration testing suite and security audit framework designed to identify and exploit vulnerabilities in web applications. It functions as a vulnerability scanner that crawls targets to find injection points and a fuzzer used to discover hidden endpoints and test input validation. The project distinguishes itself by providing an intercepting HTTP proxy for capturing and modifying traffic, combined with a knowledge-base driven exploitation system. It enables the execution of security exploits to gain remote shell access and supports post-exploitation activities, such as routing

OpenReplay is a session replay platform and frontend debugging suite designed to record and play back user browser sessions. It functions as a user behavior monitoring system that captures interaction patterns and technical metadata to identify conversion issues and revenue loss. The platform is distinguished by its self-hosted infrastructure model, allowing the recording and analytics pipeline to be deployed on private servers for full control over data residency. It also includes a browser co-browsing tool for real-time screen sharing and direct communication to provide immediate technical

Octelium is a zero-trust network access platform and identity-aware proxy designed to secure private HTTP, SSH, and SQL resources. It functions as a secure gateway that validates human and workload identities using OIDC, SAML, and FIDO2 passkeys before granting access to internal applications and SaaS APIs. The system is distinguished by its secretless access broker, which injects credentials—such as API keys, passwords, and AWS Sigv4 signatures—at the gateway level so users can access databases and cloud resources without managing secrets. It further specializes in AI gateway administration,

Shadowrocket is a proxy client application for mobile devices that functions as a multi-protocol proxy manager and a rule-based traffic router. It acts as a programmable network gateway, utilizing a virtual network interface to route system-level traffic through secure tunnels. The project distinguishes itself through a programmable environment that executes JavaScript scripts and modules to automate DNS resolution and handle complex network request logic. It further provides an HTTPS traffic inspector capable of decrypting encrypted traffic using custom certificates to modify headers and rew

CodeIgniter is a PHP web framework built on the Model-View-Controller pattern, designed for building full-stack web applications. It provides a lightweight toolkit with minimal configuration, organizing application logic into controllers, models, and views for clean separation of concerns. The framework includes a fluent query builder for constructing SQL statements programmatically, PSR-4 autoloading with namespace mapping, and a service-based dependency injection container for managing shared class instances. The framework distinguishes itself through its comprehensive set of built-in tools

This project provides a TypeScript software development kit for the Model Context Protocol, a standard designed to facilitate bidirectional communication between AI applications and external data sources or tools. It serves as a foundational framework for building both clients and servers, enabling language models to interact with external systems through a unified, decoupled interface. The SDK distinguishes itself by implementing a transport-agnostic connection layer that supports both local standard input-output streams and remote HTTP endpoints. It utilizes a JSON-RPC message bus to manage

brpc is a high-performance C++ RPC framework and network programming library designed for building distributed systems. It functions as a multi-protocol RPC server capable of hosting and detecting multiple communication protocols, including gRPC, Thrift, HTTP, Redis, and Memcached, on a single TCP port. The project distinguishes itself through high-throughput data transport and memory efficiency, utilizing RDMA-based transport to bypass the kernel TCP stack and zero-copy memory management to eliminate data duplication. It also implements the Raft algorithm for consensus-based state replicatio

Wireshark is a network protocol analyzer and traffic inspector used for capturing and inspecting network traffic. It functions as a packet capture tool that intercepts live data from network interfaces and a TCP/IP dissector that decodes network protocol layers to translate raw binary packets into human-readable fields. The system provides capabilities for protocol stream reconstruction, grouping related packets into cohesive conversations between endpoints. It also operates as a packet file converter, allowing for the reading, modification, and conversion of network capture files across vari

httplab is an HTTP mock server and interactive API simulator used to analyze incoming request payloads and simulate custom HTTP responses for application testing. It functions as a request inspector that captures and displays real-time details of HTTP headers and bodies sent by clients. The project includes a response management system that imports and stores predefined HTTP response templates using JSON files. This allows for the persistence of request and response configurations to local files for use in reusable testing scenarios. The tool provides capabilities for generating custom HTTP

This project is a specialized browser debugging interface designed to monitor DOM elements, network traffic, and JavaScript execution. It provides a client-side user interface for inspecting and debugging web applications, allowing for the real-time modification of CSS styles and the investigation of the JavaScript runtime. The toolkit includes dedicated analysis tools for WebAssembly, featuring disassembly highlighting, scope inspection, and binary execution profiling. It also provides a network traffic inspector for analyzing HTTP requests and a CSS style editor for testing properties and a

This project is a Node.js HTTP proxy server that enables cross-domain API requests from browsers by injecting Cross-Origin Resource Sharing headers into HTTP responses. It functions as a reverse proxy gateway and header manipulator, allowing for the interception and modification of traffic between a client and a target server. The proxy provides mechanisms to bypass browser same-origin policy restrictions through automated header injection. It includes capabilities for origin-based rate limiting and request interception to control traffic flow and prevent unauthorized usage of the proxy servi

This project is a REST mock API and e-commerce sandbox that provides simulated backend data for testing and prototyping. It serves as a JSON data provider, offering predefined endpoints to manage product catalogs, customer profiles, and shopping carts. The system uses JSON-based mock persistence and in-memory state simulation to deliver consistent data without a database. It includes a JWT authentication mock that simulates user login flows by issuing tokens to verify identity and access to protected resources. The API covers capabilities for catalog management, shopping cart operations, and

httplab is an interactive HTTP mock server, request inspection tool, and response simulator. It functions as a web server designed to capture and analyze incoming HTTP requests and headers in real time for debugging purposes. The tool enables the construction and delivery of custom HTTP responses to simulate various server behaviors. Users can forge specific headers and bodies to test how client applications handle different status codes and payloads, with the ability to save these configurations as response templates for consistent reuse across sessions. The project covers a broad surface o