Open-source alternatives to Sigil

Readest is a comprehensive digital reading platform designed to manage, annotate, and consume electronic books across multiple devices. It functions as a versatile library manager and reading environment, supporting a wide range of user needs from standard ebook consumption to specialized study and accessibility-focused workflows. The platform distinguishes itself through advanced features like parallel text study, which enables side-by-side document rendering with synchronized scrolling, and a robust text-to-speech engine that provides hands-free reading with synchronized visual highlighting

Koodo Reader is an open-source, cross-platform eBook reader designed for managing and studying digital documents. It functions as both a standalone desktop application and a self-hosted web environment, allowing users to organize their libraries and read across multiple devices. The application distinguishes itself through integrated study and annotation tools that facilitate personal knowledge management, enabling users to highlight and extract insights from their documents. It supports a consistent reading experience by synchronizing progress and notes across platforms, while also providing

iChm is a CHM reader for Mac OS X

Grav is a flat-file content management system that eliminates the need for a traditional database by storing site content and configuration in human-readable Markdown and YAML files. Built as a modular PHP web framework, it uses a hierarchical page routing system where the physical directory structure directly determines the site's URL paths. The platform is distinguished by its event-driven plugin architecture and a command-line interface that prioritizes system administration, deployment, and maintenance tasks. It utilizes a blueprint-driven system to generate administrative forms from stru

This project is a plugin-based WYSIWYG document layout engine and rich text editor that uses Canvas and SVG for rendering. It functions as a collaborative editor utilizing conflict-free replicated data types to enable real-time synchronization across multiple users. The system serves as an interactive form builder, allowing for the embedding of input controls such as checkboxes and date pickers directly into documents. It is designed for high-fidelity output, ensuring the visual representation during editing matches the final format for PDF and image exports. The editor covers broad capabili

This project is a React-based rich text editor designed for authoring and managing markdown documents through a visual interface. It functions as a modular framework that renders markdown in real-time, allowing users to create structured content without manual syntax entry. The editor is built on a plugin-based architecture that enables developers to extend functionality while maintaining minimal application bundle sizes. It provides a comprehensive command interface for programmatic content manipulation and utilizes reactive state management to ensure the visual editing surface remains synch

This project is a browser-based JavaScript library that transforms standard web elements into inline, WYSIWYG rich text editing areas. It functions as a programmatic wrapper around the native browser content-editable attribute, providing a structured interface for managing text input, media embedding, and document formatting directly within existing page layouts. The editor is distinguished by its contextual floating toolbar, which dynamically appears based on user text selection to provide relevant formatting options. It utilizes a plugin-based architecture that allows developers to inject c

LightTable is an extensible source code editor and integrated development environment designed as an interactive programming environment. It enables the evaluation of programming language fragments in real time to provide instant feedback on expressions. The workspace functions as a remote execution environment, connecting to and managing external servers to run code within remote processes. It allows for an interactive workflow where users can execute code fragments and track expression values without restarting the environment. The system provides source code editing capabilities, includin

LogicFlow is an SVG-based flowchart editing framework and visual graph editor used for building customizable business process diagrams. It serves as a customizable diagramming engine for rendering business process models, entity relationship diagrams, and unified modeling language charts. The system is characterized by a plugin-based architecture that allows developers to define specialized graphical elements and register pluggable modules. A distinctive feature is its overlay system, which positions standard HTML components on top of the SVG canvas to create interactive menus and control pan

Forem is an open-source platform designed for building and managing technical communities. It functions as a social publishing engine that enables members to share long-form content, participate in threaded discussions, and engage through social interactions. The platform provides tools for organizations to maintain branded profiles, host community hackathons, and facilitate collaborative learning through structured educational tracks. Beyond its social features, Forem integrates advanced capabilities for AI agent workflow orchestration and codebase knowledge graphing. It allows developers to

Macdown is a markdown text editor and HTML renderer designed for structured document composition. It provides a workspace for writing in lightweight markup syntax while simultaneously generating a live HTML preview of the rendered output. The editor distinguishes itself through a programmable interface, offering a command line utility to open files or pipe text directly into the application. It further supports extensibility via a plugin system that allows for the addition of custom features and functional modules at runtime. The application handles technical documentation requirements inclu

Foliate is an EPUB e-book reader and multi-format document viewer designed for reading and managing digital books. It functions as a digital library manager that indexes local files and tracks reading progress across a personal collection. The application supports complex layout handling, including right-to-left text and vertical writing with automatic hyphenation. It provides a text-to-speech interface that converts document content into spoken audio using a system speech dispatcher. The tool includes capabilities for digital text annotation, allowing users to create highlights and notes. I

Spyder is a scientific integrated development environment designed for scientific computing and interactive Python programming. It functions as a static analysis code editor and an interactive Python console, providing a specialized environment for writing and analyzing code for science and engineering. The platform distinguishes itself as an extensible development tool, utilizing a modular plugin architecture that allows for the addition of custom features or the embedding of core components into other software. It features a dedicated debugger and profiler for tracing code execution and mea

QtAV is a cross-platform media engine and multimedia framework that combines FFmpeg decoding with the Qt framework for audio and video rendering. It functions as a hardware-accelerated video player, an OpenGL video renderer, and a multimedia stream transcoder. The project distinguishes itself through a hardware-abstraction decoding layer that utilizes GPU interfaces such as VA-API and VideoToolbox to decode high-resolution video. It employs a zero-copy memory transfer path to move decoded video data directly to graphics APIs, reducing CPU overhead and enabling high-performance YUV rendering.

This project is a responsive Jekyll static site theme designed for technical blogs, documentation, and multilingual websites. It focuses on text readability and the presentation of technical content, providing a customizable CSS theme with multiple color palettes and dark mode toggling. The theme distinguishes itself through specialized rendering for technical assets, including mathematical formulas, diagrams, and syntax-highlighted code. It includes built-in internationalization support via translation keys to facilitate the creation of sites in multiple languages. The capability surface co

macOS comic viewer

Calibre-web is a self-hosted web application that provides a browser-based interface for browsing, managing, and reading digital book collections stored in a library database. It functions as a comprehensive library management system, allowing users to organize large collections, edit metadata, and perform automated content updates through a centralized administrative dashboard. The platform distinguishes itself by integrating directly with external infrastructure to extend the capabilities of a standard digital library. It supports remote storage mapping to host files on cloud providers, uti

This project is a comprehensive, community-maintained knowledge base and toolkit designed for competitive programming. It serves as a centralized repository for algorithmic theory, data structures, and mathematical techniques, providing a structured reference for informatics and collegiate programming competitions. The project distinguishes itself by integrating educational content with a robust suite of automation utilities. It provides a complete workflow for competitive programming, including tools for automated test case generation, solution verification, and direct interaction with onlin

Wagtail is an open-source content management system built on the Django web framework. It provides a structured, tree-based approach to content modeling, allowing developers to define custom page types and reusable content components that are managed through a highly customizable administrative interface. The platform distinguishes itself through its flexible, block-based content composition system, which enables editors to assemble complex page layouts dynamically. It also offers robust support for multi-site and multi-lingual environments, allowing organizations to manage distinct websites

This project is a customizable browser text editor and a schema-driven document framework designed for building React-based WYSIWYG content editors. It replaces standard text areas with a system that represents content as a structured data tree rather than flat HTML, allowing for precise manipulation and validation of documents. The framework serves as an extensible content management interface and a TypeScript UI component library. It enables the development of specialized authoring tools through a plugin system and the use of strongly typed building blocks to ensure consistency across docum

Apostrophe is an open-source Node.js headless content management system that delivers structured content through REST APIs while providing a visual in-context page editor for live editing. It is built on a module-based plugin architecture that extends CMS functionality through reusable modules, each encapsulating logic, configuration, and templates. The system uses schema-driven content modeling to define data structures and validation rules through configurable schemas and custom field types, with all content stored as flexible JSON-like documents in MongoDB. The platform distinguishes itsel

Webstudio is a visual CMS and website builder that provides a visual development environment for designing and publishing websites. It functions as an AI-powered design tool, a REST and GraphQL API client, and an atomic CSS compiler. The platform distinguishes itself through generative AI capabilities for creating layout variants and refining visual styles from text prompts. It integrates a headless CMS workflow that maps external data sources to visual components and utilizes a specialized compiler to convert design tokens into deduplicated atomic CSS for optimized page load speeds. The sys

XWiki Platform is a collaborative content management system and enterprise wiki designed for creating, organizing, and sharing structured documentation. It functions as a Java-based application framework that enables teams to build data-driven business applications directly within a web environment. By combining a flexible knowledge base with modular development tools, the platform supports both standard document management and the creation of custom, interactive software solutions. The platform distinguishes itself through a highly extensible architecture that allows for deep customization w

Publii is a local static site generator and offline content management system. It operates as a desktop application that renders content into HTML files on a local machine, removing server-side vulnerabilities and eliminating the need for a live database or active internet connection during the authoring process. The system is distinguished by a focus on privacy and search engine optimization. It includes built-in tools for GDPR compliance, such as cookie consent management and the ability to restrict third-party embeds until user consent is provided. For visibility, it automates the generati

Sanity is a headless content management platform and structured content API that stores data and delivers it via an API to any frontend or device. It functions as a real-time content studio, providing a customizable editing environment for managing digital assets and documents through a type-safe, decoupled data layer. The platform is distinguished by a graph-oriented query engine using the GROQ language to filter, transform, and retrieve structured content. It enables real-time collaborative editing with live presence indicators and a schema-driven approach to document management. The syste

edx-platform is a comprehensive learning management system designed for authoring, hosting, and delivering online courses. It functions as an LTI compliant learning platform that manages student progress and profiles while delivering educational content at scale. The system is divided into a dedicated course authoring environment for creating structured learning paths and a learner-facing platform for course delivery. It includes a centralized identity platform that provides single sign-on authentication across these components. The platform's capabilities cover online course authoring, larg

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.