Open-source alternatives to Greenlet

SQLDelight is a Kotlin database library that validates SQL schema, statements, and migrations at compile time, generating type-safe Kotlin query functions from labeled SQL files. It treats SQL as the source of truth for database definitions, catching schema errors during the build process before they reach production. The library supports multiple database dialects including SQLite, MySQL, PostgreSQL, HSQL, and H2, and generates platform-specific code for Android, iOS, JVM, and JavaScript targets. It provides a platform-specific driver abstraction that handles database connectivity difference

Comlink is a remote procedure call library that transforms message-based communication into asynchronous function calls between the main thread and web workers. It provides a proxy-based interface that allows multiple threads to interact with a single object instance without manual message handling. The project enables the execution of functions across separate browser windows, iframes, and web workers, making external calls behave like local asynchronous operations. It supports the transfer of non-cloneable data through custom serialization handlers and allows for the movement of ownership f

AlaSQL is a JavaScript SQL database engine that allows for the filtering, grouping, and joining of in-memory object arrays and JSON data. It functions as an in-memory SQL database and client-side data processor, enabling the execution of SQL statements against JavaScript arrays and external data sources in both browser and server environments. The project serves as a universal data query tool capable of performing relational joins across diverse sources, such as merging Google Spreadsheets, SQLite files, and remote APIs into a single result set. It also acts as an IndexedDB SQL wrapper, allow

This project is a collection of reference implementations and prototypes focused on routing, performance optimization, background threading, and user interface components. It serves as a sample library demonstrating the use of modern web platform features and native browser APIs. The repository provides prototypes for high-performance graphics, including 3D effects and animations rendered via hardware acceleration and CSS transformations. It includes implementation examples for client-side routing to synchronize application state with browser URLs and pattern galleries for offloading computat

Leafer UI is a high-performance HTML5 canvas rendering engine and 2D vector graphics library. It utilizes a hierarchical scene tree to manage shapes, paths, and text, providing a toolkit for building interactive canvas applications and expansive infinite canvases. The engine is designed as a cross-platform canvas toolkit that decouples core logic from the drawing API, allowing it to run across web, mobile, server, and mini-program environments. It distinguishes itself by providing specialized tools for interactive graphic editor development, including hit detection, event bubbling, and transf

Muuri is a JavaScript grid layout library and draggable UI framework used to create responsive grids with drag-and-drop reordering, sorting, and animated filtering. It features a nested grid system that allows full grid instances to be embedded inside other grid items to create hierarchical structures. The library uses a web worker layout engine to offload heavy coordinate calculations to background threads, maintaining interface responsiveness during complex rearrangements. The system provides interactive capabilities for moving items between multiple containers, filtering visibility based

async-std is a Rust asynchronous runtime and non-blocking I/O library. It serves as an asynchronous standard library, providing a set of alternatives to the core Rust library for managing concurrent tasks, networking, and file system access. The project implements a standard-library-mirrored API, offering asynchronous versions of existing synchronous types to maintain a familiar interface. This approach allows for asynchronous Rust development using an interface that reflects the ergonomics of the language's standard library. The runtime includes a task executor for scheduling and executing

Embed PDF Viewer is a browser-based PDF rendering library that uses a WebAssembly port of the PDFium engine to display documents entirely on the client side, with no server-side processing required. It provides a framework-agnostic core engine layer that manages the PDF document lifecycle, memory allocation, and WebAssembly resource cleanup, with dedicated integration hooks for React and Vue 3 that handle initialization, document loading, and reactive state management. The library offers both a pre-built, embeddable viewer that can be inserted into any web page with a single initialization ca

SVGOMG is a browser-based SVG minification tool that applies SVGO transformations entirely on the client side. It processes SVG files in a Web Worker to keep the user interface responsive, then displays the original and optimized file sizes side by side, including gzipped size estimates. The tool provides a live preview of the optimized SVG markup, rendered directly in the browser for immediate visual feedback. Users can configure which SVGO optimization plugins are enabled or disabled, set numerical precision for coordinates and transforms, and optionally pretty-print the output. Multiple op

This repository is a collection of practical code snippets and implementation patterns for Flutter and Dart. It serves as a comprehensive guide and reference for asynchronous programming, state management patterns, and UI component design. The project provides advanced language reference material covering generics, reflection, factory constructors, and null-aware operators. It also includes specific utilities for manipulating Dart collections, such as helper methods for transforming and filtering maps, lists, and iterables. The coverage extends to high-level capabilities including asynchrono

monoio is a high-performance asynchronous runtime and executor for Rust. It implements a thread-per-core concurrency model that pins tasks to specific CPU cores to eliminate synchronization overhead and data migration. The runtime leverages the io_uring interface to perform non-blocking system calls and reduce kernel-user mode memory copying. It utilizes a high-performance I/O driver and zero-copy TCP stream wrapping to manage data transfer via shared-memory buffers. The project provides capabilities for CPU core affinity management, low-latency system programming, and high-performance netwo

Livestore is a reactive state management framework that utilizes a local SQLite database to store and synchronize application data. It provides an event-sourced state store that processes typed events through materializer functions to derive and persist application state. The framework implements offline-first data synchronization using a push-pull engine and append-only event logs to maintain consistency between clients and servers. It includes a real-time presence system for tracking user activity and shared session status across connected clients. The system covers a broad capability surf

Smol is a lightweight Rust asynchronous runtime and task executor. It provides a suite of foundational tools for scheduling and executing asynchronous futures, managing background workloads, and handling non-blocking network and file operations. The project includes a compatibility layer for adapting asynchronous types and execution contexts, enabling futures to run across different runtime ecosystems. It also features a mechanism to offload synchronous I/O and CPU-intensive operations to dedicated worker thread pools to prevent runtime stalls. Its capabilities cover non-blocking network I/O

Zero-cost asynchronous programming in Rust

Spritejs is a graphics library and cross-platform 2D graphics engine designed for rendering geometric shapes and sprites across web, desktop, and mobile environments. It functions as a canvas-based sprite framework that manages elements using a document object model for positioning and styling. The project provides a web worker rendering engine that distributes graphic layers to offscreen canvases, preventing main thread blocking. It also includes a server-side graphics generator for producing visual elements and images in non-browser environments. The toolkit covers a broad range of graphic

AsyncDisplayKit is an asynchronous UI framework and performance library for iOS. It provides a collection of performant alternatives to standard views, allowing developers to build responsive interfaces by offloading layout and rendering tasks to background threads. The framework is centered around a declarative layout engine based on a flexbox model, which calculates element positions and sizes asynchronously. It utilizes a node-based abstraction to wrap native views, enabling the instantiation and configuration of UI hierarchies on background threads to prevent main thread blocking. The sy

canvas-confetti is an HTML5 canvas animation library and browser particle effect engine designed to render celebratory confetti bursts. It functions as a visual effects tool that transforms SVG paths, emojis, and text into animated particles. The library offloads heavy particle calculations to a web worker to maintain main thread responsiveness and prevent the user interface from lagging. It includes built-in support for operating system reduced motion settings, automatically disabling animations for users with motion sensitivities to ensure accessibility compliance. The system supports conf

This repository contains the HTML specification, which defines the core standards for web page structuring, content organization, and document rendering. It establishes the fundamental algorithms for state-machine-based tokenization, tree construction for the document object model, and origin-based security isolation. The specification provides a framework for defining custom elements with independent lifecycles and registries. It also details the requirements for cross-document communication, session history management, and the synchronization of interface properties with content attributes.

EmulatorJS is a WebAssembly emulation framework and RetroArch web frontend designed to run classic video game ROMs and BIOS files directly in a web browser. It serves as a web-based game emulator that executes hardware-accurate emulation cores to reproduce the behavior of various vintage home consoles and arcade systems. The project is distinguished by its ability to synchronize game states between multiple users in real time using WebRTC for browser-based multiplayer gaming. It also includes a dedicated HTML5 game embed tool that generates code snippets and isolated containers to integrate p

Node-vibrant is a JavaScript image processing library designed to extract color palettes from media assets for use in dynamic user interface theming. It functions as an automated design tool that identifies dominant and muted hues to maintain visual harmony across application interfaces. The library utilizes quantization-based color clustering and heuristic-based scoring to group pixel data into representative color sets. By offloading these computationally intensive analysis tasks to background threads, the project ensures that the main execution thread remains responsive during image proces

This project is a collection of technical demonstrations and prototypes that showcase various HTML5 APIs, multimedia capabilities, and web standard implementations. It serves as a frontend technology sandbox and a gallery of implementation proofs-of-concept for modern browser features. The collection includes specialized showcases for HTML5 multimedia, featuring the manipulation of audio, video, and real-time media streams. It also provides a series of experiments focused on prototyping web capabilities to verify technical feasibility and browser support in live environments. The project cov

Node.js is an open-source, cross-platform JavaScript runtime environment built on the V8 engine, designed for executing JavaScript code outside a web browser. It operates as a server-side JavaScript platform with an event-driven, non-blocking I/O architecture that enables building scalable network applications and web servers. The runtime integrates the CommonJS module system for synchronous module loading and the npm ecosystem for sharing and reusing packages. The platform provides comprehensive capabilities for web server development, including creating HTTP and HTTPS servers, managing HTTP

This project is a PHP implementation of the Promises/A+ specification, providing a library for managing asynchronous operations and deferred values. It serves as an asynchronous task coordinator that allows for the creation of non-blocking code through a promise-based pattern. The library enables the simulation of asynchronous coroutines, allowing non-blocking code to be written in a linear style. It features duck-typed interoperability, which allows it to integrate with any foreign object that implements a then method regardless of class inheritance. The project covers broader capabilities

This project is a browser-based digital audio workstation that provides a professional-grade environment for composing, arranging, and editing musical tracks. It functions as a complete audio sequencer, enabling users to manipulate digital audio signals and construct complex musical compositions directly within a web browser. The platform distinguishes itself through a cloud-synced architecture that stores musical projects on remote servers, ensuring that creative work remains accessible and synchronized across multiple devices. By leveraging the browser as a primary workspace, it facilitates

This project is a technical interview preparation resource focused on JavaScript. It provides a collection of common technical questions, detailed answers, and conceptual quizzes designed to help users master core language fundamentals and browser APIs. The resource utilizes an interactive infrastructure that includes a coding workspace with in-browser runtime execution and an automated test suite to validate code correctness. It organizes content through curated learning paths and modular concept mapping to decompose complex language fundamentals into searchable study modules. The curriculu

Pagefind is a static site search engine that indexes HTML files to provide a browser-based search experience without the need for a backend server or API. It consists of a multilingual search indexer and a set of prebuilt, customizable user interface components for rendering search inputs and result lists. The system is designed for global content, utilizing a multilingual search indexer that detects page languages and creates independent index bundles to provide language-specific stemming and results. It further optimizes performance by using a compressed index and offloading query execution

re-frame is a functional framework for building single-page applications in ClojureScript. It provides a centralized, immutable database that serves as the single source of truth for the entire application state, enforcing a strict unidirectional data flow where events trigger state transitions and subsequent view updates. The framework distinguishes itself through a reactive signal graph and an interceptor-based middleware pipeline. By treating application logic as a sequence of data-driven events and declarative side effects, it decouples business logic from the view layer. This architectur