Dillo is a fast, lightweight, and multi-platform graphical web browser designed to operate efficiently on resource-constrained hardware and perform well over slow or unreliable network connections. Originally developed to promote the democratization of internet information access, the project emphasizes high software efficiency, user privacy, and strict adherence to web standards. The browser is written in C and C++, utilizing the FLTK (Fast Light Toolkit) library for its user interface to maintain a small memory footprint and rapid rendering speeds. It is free software licensed under the GPLv3, and it supports major operating systems including Linux, BSD, macOS, and Windows via compatibility layers.

Functionality-wise, Dillo acts as a minimalist web browser that provides a core engine for rendering HTML and CSS, while offloading additional complex functionality to a modular plugin architecture. It natively supports basic protocols like HTTP, HTTPS, and FTP, and renders various image formats including PNG, JPG, GIF, SVG, and WebP. By design, Dillo does not include a JavaScript engine, which significantly improves security and privacy while reducing the resource burden of modern, script-heavy web pages. It includes a built-in 'bug meter' to help developers identify and rectify non-standard HTML nesting or syntax errors, encouraging webmasters to create content that remains interoperable and accessible across a wider range of devices.

Some of the key features are:

• Multi-platform support: Runs natively on various Unix-like systems and can be compiled for constrained environments.
• Low Resource Usage: Optimized for high performance on old hardware and low-bandwidth connections.
• Modular Plugin System: Extensible via simple scripts or programs that communicate using standard I/O (DPI protocol).
• Privacy-Centric: Disables cookies by default and lacks JavaScript, effectively mitigating many common tracking vectors.
• Standards Compliance Tooling: Integrates a built-in bug meter to assist in validating HTML and CSS standards compliance.
• Customizable Configuration: Extensive support for local configuration files to manage proxy settings, ad-blocking, and display preferences.

Dillo functions through a lightweight core-and-plugin model. While the primary browser executable handles the core rendering tasks and user interaction, specialized tasks are managed by external plugins under the Dillo Plugin Interface (DPI) framework. Users interact with the interface using a standard desktop mouse and keyboard, with a variety of shortcuts for navigation and page management. The browser maintains a persistent, plain-text configuration system, allowing advanced users to tune behavior through simple configuration files such as dillorc and cookiesrc. When a user navigates to a new page, the core engine parses the HTML and CSS and presents the content, while the plugin system fetches resources for non-standard protocols like Gemini, Gopher, or IPFS as needed.

Some common use cases include:

• Low-End Hardware Browsing: Utilizing the browser on vintage machines, embedded systems, or Raspberry Pi-style devices where modern browsers are too heavy.
• Secure Research: Accessing the web in high-security environments where the absence of JavaScript significantly reduces the attack surface against malicious scripts.
• Minimalist Web Development: Testing the accessibility and standards compliance of web designs by viewing pages in an environment that does not rely on scripting engines.
• Alternative Protocol Access: Browsing content on the decentralized web using protocols like Gemini, Spartan, or IPFS via dedicated, easily-configured plugins.