Primer CSS Details Last Updated : 23 Jul, 2025 Comments Improve Suggest changes Like Article Like Report Primer CSS is a free open-source CSS framework that is built upon a GitHub design system to provide support to the broad spectrum of GitHub websites. It creates the foundation of the basic style elements such as spacing, typography, and color. This systematic method makes sure our patterns are steady and interoperable with every other. Its approach to CSS is influenced by Object-Oriented CSS principles, functional CSS, and BEM architecture. It is a highly reusable model.Primer CSS Details Classes are made in order to improve the behavior of the default HTML Details component.Primer CSS Details Classes:Fullscreen click area: The .details-overlay class is used to add to the <details> tag to expand the click area to the whole page. This means the user can click anywhere on the page to close the opened details tag.Darkened fullscreen click area: The .details-overlay-dark class is used to add to the <details> tag to make its background dark.Custom caret: The .details-reset class when added to the <details> tag, removes the default caret placed on the left of the details. We can then add our custom caret after using this class to the <details> tag.Using button styles with the details summary element: The .dropdown-caret class is used to add a dropdown caret icon to the <details>.Syntax:<details class="DetailsClass"> <summary class="..">..</summary></details>Example 1: In this example, we have created a simple detail with a dropdown caret icon in the summary. HTML <!DOCTYPE html> <html lang="en"> <head> <meta charset="UTF-8"> <meta name="viewport" content="width=device-width, initial-scale=1.0"> <link rel="stylesheet" href= "https://unpkg.com/@primer/[email protected]/dist/primer.css" /> <title>Primer CSS Details</title> </head> <body> <h1 style="color: green;"> GeeksforGeeks </h1> <h3>Primer CSS Details</h3> <div class="m-2"> <details class="details-overlay"> <summary class="btn btn-primary"> Click Me <span class="dropdown-caret"></span> </summary> <div class="border p-3 mt-2"> This is the sample text that will be shown when the "Click Me" text is clicked. </div> </details> </div> </body> </html> Output: Example 2: In this example, we have created a detail with a dark overlay. It means that whenever we clicked, the background becomes dark. HTML <!DOCTYPE html> <html lang="en"> <head> <meta charset="UTF-8"> <meta name="viewport" content="width=device-width, initial-scale=1.0"> <link rel="stylesheet" href= "https://unpkg.com/@primer/[email protected]/dist/primer.css" /> <title>Primer CSS Details</title> </head> <body> <h1 style="color: green;">GeeksforGeeks</h1> <h3>Primer CSS Details</h3> <div class="m-2"> <details class="details-overlay details-overlay-dark"> <summary class="btn btn-primary"> Click Me</summary> <div class="border p-3 mt-2"> This is the sample text that will be shown when the "Click Me" text is clicked. </div> </details> </div> </body> </html> Output: Comment More infoAdvertise with us Next Article CSS Introduction S saikatmohanta43434 Follow Improve Article Tags : Web Technologies CSS Primer-CSS Primer-CSS Utilities Similar Reads CSS Tutorial CSS stands for Cascading Style Sheets. It is a stylesheet language used to style and enhance website presentation. CSS is one of the three main components of a webpage, along with HTML and JavaScript.HTML adds Structure to a web page.JavaScript adds logic to it and CSS makes it visually appealing or 7 min read CSS Introduction CSS (Cascading Style Sheets) is a language designed to simplify the process of making web pages presentable.It allows you to apply styles to HTML documents by prescribing colors, fonts, spacing, and positioning.The main advantages are the separation of content (in HTML) and styling (in CSS) and the 4 min read CSS Syntax CSS is written as a rule set, which consists of a selector and a declaration block. The basic syntax of CSS is as follows:The selector is a targeted HTML element or elements to which we have to apply styling.The Declaration Block or " { } " is a block in which we write our CSS.HTML<html> <h 2 min read CSS Selectors CSS Selectors are used to target HTML elements on your pages, allowing you to apply styles based on their ID, class, type attributes, and more. There are mainly 5 types of selectors.Basic CSS Selectors: These are used to target elements by tag, .class, or # ID for fundamental styling needs.Combinato 7 min read CSS Comments CSS comments are used to add notes or explanations to your code, helping you and others understand it better. They start with /* and end with */ and can be used for both single-line and multi-line comments. Note: Comments are ignored by browsers, so they won’t affect how your webpage looks or works. 2 min read CSS Colors CSS colors are used to set the color of different parts of a webpage, like text, background, and borders. This helps make the page look more attractive and easier to read. You can define colors using names, hex codes, RGB values, and more.You can try different formats of colors here- #content-iframe 5 min read CSS Borders Borders in CSS are used to create a visible outline around an element. They can be customized in terms ofWidth: The thickness of the border.Style: The appearance of the border (solid, dashed, dotted, etc.).Color: The color of the border.You can try different types of borders here- #custom-iframe{ he 5 min read CSS Margins CSS margins are used to create space around an element, separating it from neighboring elements and the edges of the webpage. They control the layout by adjusting the distance between elements, providing better organization and readability.Syntax:body { margin: value;}HTML<html> <head> 4 min read CSS Height and Width Height and Width in CSS are used to set the height and width of boxes. Their values can be set using length, percentage, or auto.Width and HeightThe width and height properties in CSS are used to define the dimensions of an element. The values can be set in various units, such as pixels (px), centim 4 min read CSS Outline CSS outline is a property used to draw a line around an element's border. It does not affect the layout, unlike borders. It's often used to highlight elements, providing a visual emphasis without altering the dimensions of the element.Syntaxselector{ outline: outline-width outline-type outline-color 4 min read Like