Open-source alternatives to Sumatrapdf

DesktopEditors is an office suite application designed for creating and editing text documents, spreadsheets, and presentations across different operating systems. It serves as an OOXML compatible editor, ensuring that files are read and written according to Office Open XML standards for cross-platform document exchange. The suite functions as a collaborative document platform featuring real-time co-authoring, version tracking, and integrated communication tools. It also acts as an AI-powered document assistant and PDF editor, providing capabilities for content generation, automated spreadshe

epub.js is a JavaScript library for parsing and displaying EPUB files within a web browser. It functions as a digital publication layout engine and rendering library that enables the creation of browser-based eBook readers with support for both paginated spreads and continuous scrolling. The project provides a specialized framework for interactive eBook annotation and precise location tracking. It uses Content Fragment Identifiers to represent text positions as unique strings, allowing for stable bookmarking, text highlighting, and note-taking. The library covers a broad range of capabilitie

kkFileView is a Spring Boot-based file preview server that provides a universal document viewer for rendering office files, PDFs, images, and 3D models directly in a web browser. It functions as a secure document rendering service that allows users to view a wide variety of file formats without requiring local software installations. The project distinguishes itself through specialized CAD to SVG conversion, transforming complex drawings into web-compatible formats. It includes a RESTful file preview API that allows these rendering capabilities to be integrated into external business applicat

Calibre is a comprehensive suite for digital library management, serving as a centralized hub for organizing, converting, and editing e-book collections. It functions as a multi-purpose platform that combines a relational database for metadata tracking with a powerful processing engine capable of transforming document formats and restructuring internal markup. Beyond local management, the software acts as a content server, enabling users to host their libraries over a network for remote access and reading via standard web browsers. The project distinguishes itself through its deep extensibili

mdBook is a documentation build system and static site generator designed to compile collections of Markdown files into structured, navigable web-based books. It provides a comprehensive framework for managing technical documentation, featuring a hierarchical table of contents, integrated full-text search, and automated build processes that transform source content into ready-to-deploy HTML websites. The project distinguishes itself through a highly modular pipeline architecture that supports custom preprocessors and swappable rendering backends. This allows authors to intercept and modify co

30dayMakeOS is an educational hobby operating system project designed for the x86 architecture. It implements a monolithic kernel and a custom bootloader that transitions the CPU from real mode to 32-bit protected mode to enable flat memory addressing. The project focuses on low-level system development, featuring a custom graphics driver for direct pixel-buffer rendering and window management without an existing operating system. It includes an x86 bootloader that loads the kernel from disk into memory. The system covers core kernel capabilities including round-robin task scheduling for pro

qpdf is a collection of specialized utility tools for the structural transformation, metadata inspection, file optimization, and cryptographic management of PDF documents. It provides a command line tool for transforming and inspecting internal PDF structures, a structural transformer for reorganizing pages and merging documents, and an encryption engine for managing passwords and restrictions. The project distinguishes itself through a technical approach to document manipulation, utilizing an object-based structural representation to modify files as a graph of unique objects. It includes a m

OS.js is a browser-based desktop environment built entirely with JavaScript that runs a full graphical interface with windows, file management, and applications inside any modern web browser without requiring local software installation. It provides a web desktop platform that manages application windows as DOM elements with z-ordering, resizing, and event routing, while offering an abstracted virtual filesystem layer that unifies access across multiple storage backends through a common read/write interface. The platform connects to remote servers and desktops using SSH, VNC, or Xpra protocol

Radare2 is a comprehensive framework for reverse engineering and analyzing compiled software. It provides a command-line environment designed for disassembling, debugging, and patching binary executables across a wide range of processor architectures and operating systems. The system distinguishes itself through a modular, plugin-based architecture that supports cross-platform analysis and automated workflows. It utilizes memory-mapped file access to enable efficient structural inspection and modification of binaries without requiring full file loads. By lifting machine instructions into a un

Karma is a JavaScript test runner designed for executing test suites across multiple real web browsers to ensure cross-browser compatibility. It functions as a browser-based execution system that launches browsers, captures console output, and provides a command line interface for running automated tests within continuous integration pipelines. The project utilizes a plugin architecture that allows for the integration of third-party launchers, reporters, and preprocessors. It employs an adapter-based framework to execute tests from various assertion libraries through a unified runner interfac

Checkstyle is a Java static analysis tool and linter designed to identify and enforce coding standards and best practices. It functions as a code quality auditor and Javadoc validation tool, checking source code against configurable rulesets to ensure structural and stylistic consistency. The project allows for the creation of custom linting rules by extending a core API to inspect the abstract syntax tree. It further enables specialized validation through the use of XPath expressions to query the syntax tree for specific code patterns and violations. Capability areas include the enforcement

ktlint is a linter and code formatter for Kotlin that checks source files against a built-in set of style rules and automatically rewrites them to match those rules. It operates by walking the Kotlin abstract syntax tree, detecting violations, and applying transformations directly at the node level before regenerating the source code from the modified tree. The project ships a curated default rule set that requires no configuration to enforce consistent formatting, and provides a command-line interface for running linting and formatting in batch mode. Its rule-set-based plugin architecture al

TinyMCE is a JavaScript rich text editor and WYSIWYG HTML editor that provides a visual interface for creating and formatting content within web applications. It functions as an extensible editor framework and web content management UI, allowing users to author and style documents through a browser-based interface. The project is distinguished by a plugin-based extension system and a public API that enable the addition of custom capabilities and modifications to the visual interface. It utilizes a framework-agnostic core, providing dedicated integration for React, Vue, and Angular. The syste

This project is a web-based collaborative editor and scientific document management system designed for LaTeX. It provides a centralized environment for writing, editing, and compiling academic manuscripts, enabling multiple users to work on the same project simultaneously through real-time synchronization. The platform distinguishes itself by treating documents as version-controlled repositories, allowing for granular history tracking and bidirectional synchronization with external version control systems. It features a secure, containerized compilation pipeline that isolates build processes

This project is a community-curated directory of open-source software designed for deployment in private server environments and home labs. It serves as a comprehensive resource for discovering independent, self-hosted alternatives to mainstream cloud services, enabling users to maintain full data ownership and control over their digital infrastructure. The directory is structured through a hierarchical taxonomy that organizes a vast collection of applications into logical categories, ranging from media management and data analytics to private communication and team productivity tools. It dis

eSearch is a desktop tool that combines screen capture, image annotation, screen recording, optical character recognition (OCR), and text search and translation into a single application. It is built around a modular architecture that coordinates these tasks through an event-driven capture pipeline, allowing users to capture screen regions, annotate them with drawing and shape tools, and then extract text using a local-first OCR engine or optional cloud services. The project distinguishes itself by integrating a command-line interface for triggering capture and recognition tasks, enabling scr

This project is a Chromium-based mobile browser and rendering engine designed for mobile platforms. It functions as a web extension host, allowing the execution of browser extensions within a mobile environment to provide custom functionality. The project distinguishes itself through custom user interface modifications, such as the implementation of a specialized night mode and the relocation of the address bar for improved ergonomics. It also includes a remote debugging interface and protocol that allow an external developer console to connect to a live browser instance for inspecting and tr

Navidrome is a self-hosted music streaming server designed to organize, index, and stream personal digital music collections. It functions as a centralized audio streaming platform that manages local audio files, automatically enriching them with metadata and artwork while providing a web interface for playback. The system supports multi-user access, allowing administrators to manage separate collections and listening histories with granular permissions. The platform distinguishes itself through its compatibility with the Subsonic API, enabling users to connect a wide range of third-party mus

pdf2docx is a suite of PDF utilities designed to transform static PDF documents into editable DOCX files. It functions as a multi-core processor capable of accelerating the conversion of large files by distributing page tasks across multiple CPU cores. The project includes specialized tools for decrypting password-protected PDF files and extracting tabular content as structured data. It also provides a layout analyzer to visually inspect and verify document structure during the conversion process. Conversion is accessible through both a graphical user interface and a command-line interface,

This project is a JVM testing framework that provides a foundation for defining and running automated tests using a pluggable engine architecture. It functions as a JVM test orchestrator and a modular test engine API, allowing multiple testing engines to be grouped and executed as a single coordinated unit. The framework includes a platform launcher for discovering and executing test suites from build systems, integrated development environments, or the command line. It enables the creation of custom testing frameworks through a standardized interface that integrates into a shared execution p

Redox is a POSIX-compliant, microkernel-based operating system written entirely in Rust. By utilizing a memory-safe language for the kernel and all system components, the project eliminates common vulnerabilities such as buffer overflows and use-after-free errors. Its architecture relies on a minimal kernel that manages only essential hardware and process isolation, delegating all other system services to unprivileged user-space processes. The system distinguishes itself through a modular design where hardware drivers and system services run as independent user-space daemons, allowing them to

Shimmy is a local large language model inference engine and server that loads and serves GGUF formatted weights. It is distributed as a single binary runtime written in Rust, providing a standalone environment for running models without external runtime dependencies. The project utilizes WebGPU for hardware acceleration, allowing model compute kernels to execute across diverse graphics hardware through a standardized interface. It features a local server that implements an OpenAI-compatible API layer, enabling applications to interface with local models via standardized REST endpoints. Memor

TextMate is a programmable text editor designed for software development and project management. It functions as a highly customizable environment where users can define language-specific behaviors, syntax highlighting rules, and automated workflows to suit their individual development needs. The editor distinguishes itself through a modular, bundle-based extensibility model that allows for deep integration with system shell commands. By piping document buffers through external scripts and command-line tools, users can perform complex text transformations, automate file lifecycle tasks, and b

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.

Excelize is a library for reading and writing spreadsheet files in the Office Open XML format. It provides a comprehensive suite of tools for programmatically creating, modifying, and analyzing workbooks, worksheets, and cell data, ensuring compatibility across various office software suites through structured XML serialization. The library distinguishes itself with a built-in formula calculation engine that evaluates complex mathematical and logical expressions directly against workbook data. It also features a memory-mapped streaming architecture, which allows for the efficient processing o

Notepad3 is a lightweight Windows text editor designed as a replacement for the default system notepad. It is built on the Scintilla text engine to provide source code editing capabilities, including syntax highlighting, code folding, and automatic indentation. The editor is distinguished by its support for registry-free portable execution, allowing the application to run from removable storage without system installation. It features integrated file encryption and decryption tools for secure document management and a regular expression engine for complex search and replace operations across

This project is a desktop screen capture and annotation utility designed for Linux environments. It provides an interactive graphical overlay that allows users to select specific screen regions, apply visual annotations such as shapes, text, and pixelation, and manage the resulting images through a configurable post-capture pipeline. The application distinguishes itself through deep system integration and automation capabilities. It operates as a persistent background daemon that monitors global hotkeys and supports inter-process communication via a system message bus, enabling users to trigg