Key Facts
- ✓ The guide is titled 'Show HN: An interactive guide to how browsers work'
- ✓ It was published on January 4, 2026
- ✓ The resource is available at the URL https://howbrowserswork.com/
- ✓ The guide has been discussed on the Y Combinator news platform
Quick Summary
A new interactive guide has been released that explains the complex internal mechanics of web browsers. The resource is designed to provide a comprehensive technical breakdown of the processes that occur when a user interacts with a web browser.
The guide covers the entire lifecycle of a web request, starting from the moment a URL is entered. It details the initial network steps, including DNS resolution and TCP/IP connections, before moving on to the secure handshake protocols required for HTTPS.
Furthermore, the guide explores how browsers process the data they receive. It explains the parsing of HTML to construct the Document Object Model (DOM), the handling of CSS for styling, and the final rendering steps that display the page to the user. This resource serves as a visual and interactive tool for understanding the fundamental technologies that power the modern web.
Network Connectivity and Protocols
The guide begins by detailing the network phase of loading a web page. When a user types a web address, the browser must first resolve the domain name to an IP address. This process, known as a DNS lookup, is the first step in establishing a connection.
Once the IP address is known, the browser initiates a connection to the server. The guide explains the TCP three-way handshake (SYN, SYN-ACK, ACK) required to establish a reliable connection. For secure sites, it also covers the TLS handshake that encrypts the data transfer.
These initial steps are crucial for setting up the communication channel between the client and the server. The interactive nature of the guide allows users to visualize these invisible background processes that happen in milliseconds.
Parsing and DOM Construction
After the connection is established and the server responds, the browser begins processing the HTML data. The guide illustrates how the browser parses the raw bytes of data into characters, then tokens, and finally nodes.
These nodes are assembled to form the Document Object Model (DOM), which represents the structure of the page in a way that the browser can understand and manipulate. The guide highlights how the construction of the DOM is interleaved with the discovery of external resources.
As the parser encounters references to images, scripts, and stylesheets, it requests these resources. The guide explains the critical path of rendering and how different types of resources can affect the speed at which the page becomes visible to the user.
Rendering and Painting
The final stage covered in the guide is the rendering process. Once the DOM is constructed, the browser begins to calculate the styles for each node. This creates the Render Tree, which includes only the visual elements required for display.
The guide details the Layout (or Reflow) step, where the browser calculates the exact position and size of each element on the screen. Following the layout, the browser performs the Paint operation, converting the render tree into actual pixels on the display.
By breaking down these complex algorithms into interactive visualizations, the guide provides a clear view of how static code is transformed into a dynamic, interactive web page. It serves as an educational tool for understanding browser optimization and performance.
