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

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

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

zip.js is a JavaScript library designed for creating, reading, and extracting ZIP archives directly within a web browser. It provides a comprehensive toolkit for managing compressed files and encrypted data storage entirely on the client side, eliminating the need for server-side backends or external dependencies. The library distinguishes itself by utilizing the Web Streams API and multi-core processing to handle large datasets efficiently. By offloading heavy compression and decompression tasks to background worker threads, it ensures that the browser interface remains responsive during int

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.

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

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

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

Starboard Notebook is a web-based environment designed for literate programming and interactive code execution. It functions as an in-browser notebook system that allows users to combine formatted text with executable code blocks, enabling the creation of dynamic documents and data visualizations without requiring a backend server. The platform is built as an embeddable runtime, allowing developers to integrate interactive, cell-based documentation directly into existing web pages. It distinguishes itself through a modular architecture that supports custom plugin development, enabling the reg

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

Zero-cost asynchronous programming in Rust

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

Parallel.js is a JavaScript library for running computational tasks concurrently across background worker threads and multi-core environments in browsers and Node. It wraps web worker management into a framework that offloads heavy computations without blocking the main event loop. The library initializes parallel jobs by wrapping serializable data in memory and configuring worker threads, execution timeouts, and synchronous fallback behavior. It supports mapping functions across datasets and reducing dataset values to scalar results by distributing work across separate threads. Operations ex

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

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

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

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

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

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

Async-task is a low-level Rust concurrency library and asynchronous task executor designed for building custom asynchronous runtimes and managing background task execution pipelines. It provides concurrency primitives that handle atomic task state management, heap-allocated futures, output retrieval, and type-erased execution handles. The library coordinates task execution, cancellation, and polling states across multiple threads using lock-free atomic operations and reference counting. Developers can supply custom scheduling logic and metadata hooks that dictate when and how tasks are queue

Javascript Playgrounds is a browser-based code execution engine designed for running untrusted JavaScript snippets and managing interactive playgrounds. The system isolates user-submitted code inside dedicated web workers to prevent main thread blocking and protect the host environment, while supporting dynamic module loading that fetches external libraries and third-party scripts on demand. The platform includes architectural tools for mobile device simulation, rendering application output inside configurable viewport wrappers with adjustable platform dimensions and status bar styling. Debug

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

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

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