Open-source alternatives to Postcat

Prism is a set of tools for generating mock servers and validation proxies based on OpenAPI specifications or Postman collection files. It serves as an API contract testing tool to verify that API implementations adhere to formal contracts. The project provides an OpenAPI mock server that simulates API responses and a validation proxy that checks live HTTP traffic against an OpenAPI specification to identify implementation discrepancies. It also includes a mock server capable of mimicking API behavior based on exported Postman Collection files. The tool covers API behavior simulation and tra

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

This project is a multi-protocol API simulation and mocking system designed to replace external dependencies during development and testing. It provides an API mocking server, a network traffic proxy, and specialized simulators for language model services and identity providers. The system distinguishes itself through deep AI simulation capabilities, including the emulation of language model providers and Model Context Protocol servers using JSON-RPC 2.0. It supports multi-turn conversational logic, state tracking for AI chat APIs, and the visualization of agent execution through call graphs

Insomnia is a desktop application designed for the design, testing, and debugging of network requests. It serves as a comprehensive environment for managing the API lifecycle, allowing users to draft interface specifications, simulate endpoints, and execute automated testing workflows within continuous integration pipelines. The platform distinguishes itself through a modular, plugin-based architecture that enables the integration of custom scripts and external tools. It supports complex development needs by providing a local-first data persistence model, environment-variable substitution for

Insomnia is a cross-platform API development environment that integrates a request debugger, schema design tools, a mocking server, and a test automation framework. It provides a unified workspace for sending requests and analyzing responses across REST, GraphQL, gRPC, and WebSocket protocols. The platform enables the design and preview of API specifications through a visual editor and allows for the simulation of backend behavior using mocking tools. It supports organizing and synchronizing API collections via local storage, cloud synchronization, or Git. The suite includes a command-line i

This is a desktop HTTP client application used for constructing, sending, and analyzing HTTP and GraphQL requests. It provides a graphical interface for API development and testing, including a dedicated GraphQL client with schema-driven autocomplete and validation. The project features an integrated AI assistant that generates API requests from natural language prompts. It supports a complex organization system of spaces and collections with hierarchical authentication inheritance and recursive variable resolution for dynamic request values. The tool covers a broad range of capabilities, in

Swagger Editor is a web-based authoring tool and development environment used to design, document, and validate API specifications. It specifically supports the OpenAPI Specification, providing a browser interface for writing API schemas and verifying their structure. The tool features real-time rendering that produces a visual preview of the API documentation as the specification is edited. It includes syntax highlighting based on standardized schemas to improve the readability of the API definitions. The editor supports importing specifications from files, external URLs, or example fixture

Reqable is a cross-platform network debugging tool that functions as an HTTP/HTTPS debugging proxy, a REST API client, and a traffic replay tool. It captures, inspects, and modifies live traffic using a local MITM proxy engine, supports VPN tunnel capture for mobile devices, and provides a Python scripting sandbox for custom traffic processing. The application is available on Windows, macOS, Linux, iOS, and Android. The tool distinguishes itself by combining traffic interception with breakpoint-based request modification, allowing users to pause live HTTP traffic for manual inspection and alt

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

Karate is an end-to-end testing framework and API test automation tool used to validate REST and SOAP APIs, drive browser interactions, and measure system performance. It functions as a unified solution for executing automated tests across both API backends and web frontends. The framework utilizes a custom domain specific language and Gherkin-style feature mapping to define requests and assertions. It includes an API mocking server to simulate backend responses, enabling development and integration testing without live dependencies. The tool covers a broad range of functional testing catego

Postman is an API platform that enables users to build, test, and interact with APIs by sending HTTP requests and viewing responses directly within the tool. It provides a graphical interface for designing and managing sequences of API interactions, allowing users to create and organize related API requests into named collections for reuse and sharing. The platform supports automating API workflows through test scripts and built-in sequences, and facilitates collaboration by enabling teams to share collections, specifications, and workflows. Users can document APIs by attaching descriptions a

Showdoc is a technical documentation platform and knowledge management system designed to centralize project specifications, internal manuals, and technical guides. Built as a PHP web application, it provides a collaborative environment for teams to organize and share information across software development organizations. The platform distinguishes itself through its ability to automate documentation workflows by parsing source code comments and synchronizing technical records with the current state of a codebase. It also features specialized tools for managing RESTful API documentation and g

Hearthstone Deck Tracker is a gaming companion application and collection manager for Windows. It serves as a game utility for tracking real-time gameplay data, managing card collections, and analyzing deck performance through match history and win rates. The application features a plugin-based architecture that allows for the addition of third-party logic to introduce custom tracking behaviors and automation triggers. For broadcasters, it provides a chroma-key compatible streaming overlay to display real-time game data on live video feeds. Its capabilities include importing deck lists from

This project provides a suite of interfaces and tools for accessing electricity carbon intensity and production metrics. It includes an API for real-time and historical data, a geographic power data map for visualizing regional carbon intensity and renewable energy percentages, and a system for extracting datasets required for standardized greenhouse gas emissions reporting. The project features an interactive API sandbox that allows users to test requests and inspect data responses without writing code. It also includes mechanisms for institutional email verification to manage access to hist

Cerebro is a desktop application launcher and search interface that provides a minimalist overlay for finding files, launching software, and executing web queries. It functions as a centralized command bar designed for desktop productivity and rapid system navigation. The project features an extensible plugin framework and a modular architecture, allowing third-party add-ons to integrate new tools and capabilities through a standardized API. It also includes a customizable theme engine that enables users to adjust the visual appearance and styles of the workspace interface. The interface sup

Apache JMeter is a Java-based performance testing tool and multi-protocol traffic simulator used to analyze the stability and scalability of servers and networks. It functions as a distributed load testing framework that coordinates remote worker nodes from a single controller to generate high volumes of concurrent traffic. The project is distinguished by its ability to simulate traffic across diverse backend systems, including HTTP, JDBC, LDAP, JMS, FTP, and TCP. It provides a headless command-line interface for automated execution and a reporting system that transforms raw sample logs into

This project is an API documentation management platform and mocking server. It provides a central system for organizing API specifications and managing metadata to maintain consistency across the development lifecycle. The toolset includes a mocking engine that generates simulated backend responses, allowing frontend development to proceed without a live backend service. It also functions as a static documentation generator that converts dynamic API specifications into offline files for distribution and archival. The platform is delivered as a containerized toolset, packaging the server and

Blade is a lightweight Java MVC web framework built on an embedded Netty server. It packages the entire web application into a single executable JAR that starts the server on launch, following the MVC pattern with fast request routing and minimal configuration. The framework supports plugin-based extensibility, allowing third-party modules to add features like template rendering and static asset serving. The framework distinguishes itself through lambda-style route registration, where routes are defined using lambda expressions that map HTTP methods and URL patterns directly to handler functi

Bruno is a local-first API client designed for building, testing, and managing network requests across a wide range of protocols. By storing all collections and configurations as plain-text files directly on the local filesystem, it enables native version control and offline access, ensuring that project data remains under user control without requiring cloud synchronization. The platform distinguishes itself through a declarative approach to API management, utilizing a domain-specific language to define request parameters and metadata. This architecture supports a robust testing environment

Gatus is a multi-protocol health checker and automated service alerting tool. It provides a monitoring dashboard for tracking the uptime and health of HTTP, TCP, DNS, and gRPC endpoints, and serves as a Prometheus metrics exporter to track response times and success rates. The project distinguishes itself with a developer-oriented approach to status pages, securing administrative access and dashboards via OpenID Connect and Basic Authentication. It supports complex network environments through SSH tunneling to monitor internal services via bastion hosts and allows remote agents to push health

Coze Studio is a development platform for building intelligent agents and conversational applications. It provides a visual environment where users construct agents by linking workflows, knowledge bases, and custom prompts to automate complex tasks. The system functions as a central hub for managing AI model services, allowing developers to connect various providers to serve as the intelligence layer for their applications. The platform distinguishes itself through a node-based workflow orchestrator that enables the design of automated logic sequences on a visual canvas. It includes a modular

Qor is a Go admin framework and backend toolkit used for building administrative interfaces, headless content management systems, and REST API generators. It provides a structured environment for implementing business application backends, specializing in the management of structured content and media assets. The project distinguishes itself through comprehensive multi-language content management, featuring locale-based data versioning and a dedicated system for internationalization and translation administration. It further differentiates its offering with a built-in state machine implementa

Vfox is a command-line utility designed to manage multiple programming language runtimes and development tools on a single machine. It provides a unified interface for installing, switching, and configuring software versions across different operating systems, ensuring consistent development environments. The project distinguishes itself through a modular, plugin-based architecture that allows for the integration of diverse language runtimes and utilities beyond built-in defaults. It utilizes a combination of shim-based execution, symlink management, and dynamic shell-hook environment injecti

MeterSphere is a continuous testing platform that provides a suite of tools for automating interface, performance, and functional tests within a delivery pipeline. It functions as a comprehensive system for managing the testing lifecycle, from initial case planning and execution to defect tracking and reporting. The platform distinguishes itself through the use of large language models to automatically generate functional and interface test cases from requirements. It also features a distributed performance testing engine that coordinates pools of hardware and software resources to execute hi

ZenML is an extensible machine learning orchestration framework designed to manage the end-to-end lifecycle of data pipelines and AI agent workflows. It functions as a durable orchestrator that executes machine learning tasks as directed acyclic graphs, ensuring that every step is containerized for consistent performance across local, cloud, and hybrid infrastructure. By decoupling pipeline code from underlying compute and storage backends, the platform allows developers to define infrastructure-agnostic stacks that remain portable across diverse environments. The project distinguishes itself

CoreDNS is a modular domain name system server designed for cloud-native environments. It functions as a flexible DNS resolver and forwarder that manages network traffic by routing queries based on zone-based rules and authoritative data. The server is built to integrate with service discovery systems, enabling it to map service names to network addresses within containerized infrastructure. The project is defined by a plugin-based request pipeline that allows for the extension of server functionality through custom modules. These plugins can intercept, modify, or log network requests in real