Apps to Built-in viewer

Polar is a powerful desktop application designed to serve as an integrated reading environment. It allows users to actively read, annotate PDFs and web pages, create flashcards for spaced repetition learning, organize their digital library, and track their reading and learning progress. It's built for focused and deep engagement with digital content.

Vifm is a ncurses-based file manager with Vim-like keybindings, designed for efficiency in terminal environments. It offers a dual-pane interface, tab support, and extensive customization options, making it a powerful tool for users comfortable with command-line workflows and seeking a highly keyboard-driven file management experience.

PdfMod is a user-friendly application designed for straightforward PDF document manipulation. It allows users to effortlessly rearrange, rotate, and remove pages within PDF files, as well as extract images. Focusing on simplicity, it provides a basic set of tools for essential PDF editing needs.

Sunflower is a flexible and powerful twin-panel file manager designed specifically for the Linux desktop. It offers a highly customizable interface, extensive plugin support, and a rich set of features for efficient file management, including dual-pane and multi-tab views, support for various protocols, and built-in tools.

trolCommander is a powerful and lightweight cross-platform file manager. It is a fork of the popular muCommander, offering a dual-pane interface, rich feature set including built-in viewers, terminal, FTP/SFTP support, and extensive customization options. Designed for efficiency and speed, it's an excellent alternative for users seeking advanced file management capabilities across various operating systems.

Cool Reader is a highly configurable and lightweight eBook viewer designed for comfortable reading on various devices. It supports multiple formats including EPUB and DOCBOOK, offers extensive customization options for interface and reading experience, and includes useful features like library management, annotations, and sync capabilities.

MuPDF is a lightweight, portable document rendering engine and viewer for PDF, XPS, and EPUB formats. Known for its speed and accurate rendering, it's ideal for integrating document display into various applications or for users seeking a minimalist, high-performance viewer.

Cozy is a personal cloud platform designed to give users control over their digital lives. Store, sync, and share your photos, files, contacts, and calendar in a private and secure environment. It offers a suite of integrated applications to manage your data.

Krusader is a powerful, dual-pane file manager for Unix-like operating systems, offering extensive file management capabilities, including archive handling, FTP support, batch operations, and advanced customization options. It's designed for users who need an efficient and feature-rich alternative to standard file browsers.

muCommander is a versatile, open-source file manager designed for productivity across various operating systems. It offers a dual-pane interface for efficient file operations, built-in support for network protocols like FTP and SSH, and extensive customization options, making it a powerful tool for both casual users and power users who need advanced file management capabilities.

DBeaver is a powerful, open-source database tool for developers, database administrators, and analysts. It provides a universal and intuitive interface for managing databases, writing SQL queries, generating ER diagrams, and exporting/importing data for various database systems.

QuiteRSS is a free, open-source, cross-platform RSS/Atom news feed reader featuring an integrated web browser, filtering options, notifications, and support for multiple languages. It's designed for efficient news consumption and organization.

Far Manager is a console-based file manager for Windows, offering a powerful dual-pane interface and extensive customization options. It supports keyboard shortcuts for efficient navigation and file operations, while its plugin architecture allows for significant expandability.

FBReader is a versatile and free ebook reader application supporting multiple formats including ePub, Kindle azw3, and fb2. It offers a customizable reading experience across different platforms with features like library management, synchronization, and text-to-speech.

NAPS2 (Not Another PDF Scanner 2) is a free and open-source document scanning application. It simplifies the process of scanning documents into various formats, primarily PDF, with support for OCR.

PeaZip is a free and open-source file archiver and file manager utility. It offers robust archiving capabilities supporting a wide range of formats, strong encryption options, and a built-in file explorer, making it a comprehensive tool for file compression, archiving, and security.

Calibre is a powerful and versatile open-source e-book management software that streamlines the organization, conversion, and reading of your digital book collection across various formats and devices.