Open-source alternatives to Yaak

yapi is an API management platform designed to coordinate the development of RESTful APIs between frontend, backend, and quality assurance teams. It functions as a centralized system for documenting interface specifications, simulating server responses, and validating requests through a built-in testing client. The platform features an API code generator that transforms interface specifications into typed request functions and data models across multiple programming languages. It also includes a mock server capable of generating synthetic responses using schema-based generators and rule-based

Maestro is a declarative mobile and web UI automation framework designed for end-to-end testing. It operates by querying the native accessibility tree of an application, allowing for black-box testing without requiring source code instrumentation or platform-specific dependencies. The framework distinguishes itself through a unified command syntax that abstracts interactions across Android, iOS, and web environments. It features a dynamic synchronization engine that automatically pauses test execution to account for non-deterministic animations and network-dependent content loading, ensuring

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

Thunder Client is a REST API client extension for VS Code that functions as an HTTP request manager, testing tool, and mocking workspace. It allows users to send requests, organize them into collections, and manage API configurations directly within the editor. The project distinguishes itself through a command-line interface for executing automated test suites in CI/CD pipelines and a Git-based synchronization system for sharing request collections and environment configurations across teams. It also incorporates artificial intelligence to automate the conversion of API scripts during migrat

Note-gen is an artificial intelligence-assisted note-taking application and knowledge management tool designed for local-first data ownership. It functions as a workspace that leverages language models to organize, summarize, and synthesize personal notes into structured documents while maintaining offline accessibility. The platform distinguishes itself through a multimodal workflow orchestrator that chains sequences of tasks to process text, images, and external data. By integrating vision-language models, it extracts information from visual inputs like screenshots and documents, converting

InvenTree is an open-source inventory management platform built on Django, designed for tracking parts, stock levels, and supply chain operations through a web interface and REST API. The system uses barcodes—including QR codes, 1D barcodes, and Data Matrix codes—as primary identifiers for scanning, linking, and triggering inventory actions, and extends core functionality through a Python plugin framework supporting custom actions, UI panels, barcode handlers, and scheduled tasks. The platform distinguishes itself through a comprehensive plugin-based extensibility system that allows custom in

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

grpcui is a browser-based interactive web interface and API client for executing remote procedure calls to gRPC servers. It functions as an HTTP to gRPC gateway that translates JSON payloads into binary protobuf messages, allowing users to trigger network requests and inspect responses through a visual web interface. The tool provides schema browsing and discovery capabilities by querying server reflection or loading local protobuf descriptor files to identify available services and method signatures. It uses these definitions to automatically generate dynamic input forms for constructing req

Electric is a Postgres data synchronization engine and replication proxy designed to enable local-first software. It replicates data from Postgres databases to client-side stores in real time using logical replication, allowing applications to maintain a local embedded database for offline access and low-latency updates. The system distinguishes itself by using shapes to filter and authorize specific subsets of database rows and columns before streaming them to clients or edge workers. It further supports multi-user collaboration by integrating a conflict-free replicated data type framework t

Curl is a command-line tool and portable library for transferring data across a wide range of network protocols. It functions as a unified engine that abstracts diverse communication standards, allowing users and developers to move files and information between servers using a consistent interface. The project provides both a versatile command-line client for terminal-based automation and a stable programmatic interface for integrating complex network operations into applications. The system is distinguished by its protocol-agnostic core and its ability to manage both synchronous and asynchro

Jetty is an embedded HTTP server and Java web servlet container designed to handle incoming web requests. It functions as a lightweight network server that can be integrated directly into Java applications or hardware devices, providing a runtime environment for hosting Java web applications and servlets. The project implements a multi-protocol web serving engine with support for HTTP/1, HTTP/2, and HTTP/3. It also includes a WebSocket server implementation for real-time, full-duplex data exchange between clients and servers, alongside a Java HTTP client for consuming web services. The serve

Swashbuckle.AspNetCore is an API specification tool and documentation generator for ASP.NET Core. It extracts metadata from source code and models to produce standardized OpenAPI specifications and interactive browser interfaces for exploring and testing web APIs. The project integrates a middleware component to serve these specifications and a Swagger UI for interactive API testing directly from a running application. It also provides a command-line exporter to extract specification files from application assemblies for use in CI/CD pipelines. The tool covers a wide range of capabilities in

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

GraphQL.NET is a server-side framework for building and executing GraphQL APIs within C# applications. It provides a comprehensive toolkit for schema building, a federated engine for distributed data graphs, and a subscription handler for managing real-time data streams. The project distinguishes itself with a flexible schema builder that supports both programmatic code-first definitions and declarative schema-first approaches using the standard schema definition language. It includes a dedicated federation engine to split data graphs into subgraphs and compose them into a unified gateway, as

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

HTTPie is a command-line HTTP client designed for sending requests to web services and APIs. It functions as a terminal-based web client and JSON API interface, allowing users to interact with RESTful services and download remote files directly from the console. The tool simplifies the interaction with APIs through a custom syntax for argument parsing and automatic JSON payload serialization. It includes a request debugger to verify the structure of a request before transmission and uses ANSI-based formatting to display server responses with color and indentation for improved readability. Th

This project is a cloud API governance framework and enterprise style guide. It provides a centralized set of naming and structural rules and design guidelines for RESTful interfaces to maintain architectural consistency across large-scale distributed services. The framework establishes standards for OpenAPI specifications to ensure a uniform developer experience. It also defines a versioning policy to manage service updates and prevent breaking changes for existing client integrations. The guidelines cover resource-oriented design patterns, schema-based constraint validation, and standardiz

Yaade - Yet Another API Development Environment

SoapUI is a free and open source cross-platform functional testing solution for APIs and web services.

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 high-performance, distributed API gateway designed to manage, secure, and observe traffic for microservices, serverless functions, and artificial intelligence model providers. It functions as a dynamic service proxy and cloud-native ingress controller, centralizing policy enforcement and traffic routing through a unified configuration interface that synchronizes state across multiple nodes in real time. The platform distinguishes itself through a highly extensible architecture that utilizes a high-performance scripting engine to execute modular logic directly within the requ

A free, native Apple macOS app for testing HTTP/REST endpoints

Lapce is a high-performance text editor built with Rust that utilizes hardware acceleration for fast rendering and responsiveness. It functions as a modal text editor with Vim-style keybindings to minimize hand movement, an LSP client for language intelligence, and a remote development environment for editing files and executing code on distant servers. The editor features an extensible architecture based on the WebAssembly System Interface, allowing it to execute plugins compiled to WASI for cross-language functionality. It further distinguishes itself by implementing the Debug Adapter Proto

RestSharp is a .NET HTTP client library designed for interacting with RESTful web services. It provides a high-level request wrapper and a dedicated REST API client to manage endpoints, headers, and query parameters. The library includes a serialization mechanism that automatically converts objects to and from JSON or XML formats for API payloads. It also features a system for managing API credentials and security tokens to ensure authorized access to protected remote resources. The toolkit covers broad capabilities for external web service integration, including generic type-based deseriali

HotChocolate is a GraphQL server implementation for .NET that handles queries, mutations, and subscriptions over HTTP. It provides code-first schema generation directly from C# classes and attributes, keeping the schema and business logic in sync without manual type definitions. The project also includes a GraphQL gateway that composes multiple GraphQL and REST endpoints into a single unified schema, along with a GraphQL IDE for exploring, testing, and debugging GraphQL APIs interactively. The project distinguishes itself through its comprehensive tooling ecosystem, which includes a GraphQL c