The first step in the Browser Rendering Process is HTML parsing. The browser reads, or parses, HTML text from left to right, and uses the tags to create nodes, which form the Document Object Model (DOM). This is a tree-like structure of nodes that represents the contents of the webpage.
CSS Parsing
Simultaneously with HTML parsing, the browser parses CSS text. The CSS specifies style information for the nodes, such as layout, colors, and fonts. This also results in a tree structure, known as the CSS Object Model (CSSOM) tree.
Render Tree Construction
The browser then merges the DOM and CSSOM into a 'render tree'. This tree details the visual layout of the page, confirming what will be displayed and in what style.
Layout
The browser now calculates the dimensions and position of each visible node on the page. This process is called 'layout' or 'reflow'.
Painting
The final step is 'painting', or filling in pixels. The browser rasterizes each node in the render tree into actual pixels on the screen. Some elements may be painted in multiple layers.
Composite
If elements have been painted in multiple layers, those layers are now combined together in the right order to give the final image. This is known as compositing.
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You know when you want to look at your favorite cartoon online? The thing you use is called a browser. This is like a door to the internet. It lets you see different websites like the one for your cartoon.
What a Browser Does
The browser is a bit like a magical translator. It takes all the different parts of a website, like pictures, videos, and words, and puts them together for you to see. This process of putting everything together is what we call the browser rendering process.
The Browser Rendering Process
The browser rendering process is like building a house. First, the browser gets instructions like a blueprint. This tells the browser what should be on the website and where. These instructions are written in a special language called HTML.
Then There's CSS
After the browser understands the HTML, it gets another set of instructions. This one is all about colors, shapes, and sizes. This is another special code called CSS. It’s like deciding what color to paint the walls and where to put the furniture in the house.
Final Step: JavaScript
The last code the browser gets is JavaScript. This is like magic spells that keep things fun and interesting on the website. With JavaScript, things can move around, pop up, or change when you click them.
Putting It All Together
The browser combines all the codes and scripts it got - HTML, CSS, and JavaScript. Kind of like building a toy from a Lego set. It follows the instructions step by step until the whole webpage is built and you can see and interact with it.
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You can learn more about JavaScript execution in browser rendering context here: JavaScript and the Browser Rendering Process
About author
Roman Y.
Senior Software Engineer at Nike
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