Top 10 CSS Performance Tips

Hi everyone! There are a lot of tips and tricks about CSS styling. But not in this article. Today I want to talk about how to use CSS more efficiently and make your platform faster! 1. Simple selectors CSS has a wide, flexible array of coding options you can use to target HTML elements for styling. Over the years, experts have advised developers to write simple selectors to reduce the load on the browser and keep the code clean and simple. Even the most complex CSS selectors take milliseconds to parse, but reducing complexity will reduce file sizes and aid browser parsing Do NOT: main > div.blog-section + article > * { /* Code here */ } DO: .hero-image { /* Code here */ } 2. Critical Inline CSS You can inline critical CSS rules. This improves performance by: Identifying essential styles used by elements above the fold (those visible when the page loads) Inlining that critical CSS into a tag in your Loading the remaining CSS asynchronously to avoid render blocking. This can be accomplished by loading the stylesheet in a “print” style that the browser gives a lower priority. JavaScript then switches it to an “all” media style once the page has loaded. /* critical styles */ body { font-family: sans-serif; color: #111; } 3. Avoid @import The at-rule allows any CSS file to be included within another. This appears a reasonable way to load smaller components and fonts. But it is not. @import rules can be nested so the browser must load and parse each file in series. @import Multiple tags within the HTML will load CSS files in parallel, which is considerably more efficient — especially when using HTTP/2. Do NOT: /* main.css */ @import url("style1.css"); @import url("style2.css"); @import url("style3.css"); DO: 4. Preload CSS Files The tag provides an optional preload attribute that can start a download immediately rather than waiting for the real reference in the HTML. 5. Progressive Rendering Rather than using a single site-wide CSS file, is a technique that defines individual stylesheets for separate components. Each is loaded immediately before a component is referenced in the HTML. progressive rendering Each still blocks rendering, but for a shorter time, because the file is smaller. The page is usable sooner, because each component renders in sequence; the top of the page can be viewed while remaining content loads. ... ... ... 6. Use Media Query Rendering A single concatenated and minified will benefit most sites, but sites that require a significant quantity of larger screen styles could split CSS files and load using a media query. 7. Adopt SVG Images Scalable vector graphics (SVGs) are typically used for logos, charts, icons, and simpler diagrams. Rather than define the color of each pixel like JPG and PNG bitmaps, an SVG defines shapes such as lines, rectangles and circles in XML. Simpler SVGs are smaller than equivalent bitmaps and can infinitely scale without losing definition. An SVG can be inlined directly in CSS code as a background image. This can be ideal for smaller, reusable icons and avoids additional HTTP requests. SVG example: SVG usage example: .mysvgbackground { background: url('data:image/svg+xml;utf8, ') center center no-repeat; } 8. Style SVGs with CSS SVGs can be embedded directly within an HTML document. This adds the SVG nodes directly into the DOM. Therefore, all SVG styling attributes can be applied using CSS. SVG in DOM: SVG styles: circle { stroke-width: 1em; } .mysvg { stroke-width: 5px; stroke: #f00; fill: #ff0; } The volume of embedded SVG code is reduced and the CSS styles can be reused or animated as necessary. Note that using an SVG within an tag or as a CSS background image means they’re separated from the DOM, and CSS styling will have no effect. 9. Avoid Base64 Encoding You can encode images to base64 strings, which you can use as data URIs in HTML tags and CSS backgrounds. This reduces the number of HTTP requests, but it harms CSS performance: base64 strings can be 30% larger than their binary equivalent. browsers must decode the string before an image can be used, and altering one image pixel invalidates the whole CSS file. Only consider base64 encoding if you’re using very small, infrequently changing images where the resulting string is not significantly longer than a URL. Do NOT: .background { background-image: url('data:image/jpg;base64,ABC123...'); } DO: .svgbackground { background-image: url('data:image/svg+xml;utf8, '); } 10. Short tips Replace Images with CSS Effects - defining an “image” using CSS code uses considerably less bandwidth and is easier to modify or animate later. Use Modern Layout Techniques - and . Flexbox Grid Use CSS Animations - and will always be faster than JavaScript. transitions animations Avoid Expensive Properties - some CSS requires more processing than others. border-radius box-shadow text-shadow opacity transform filter position: fixed backdrop-filter background-blend-mode P.S. Thanks for reading! More articles about frontend development: Top 9 Tips to Improve React Performance Some HTML, CSS Little Secrets In One Article Top Lesser Known HTML 5 & CSS 3 Tips and Best Practices Top 12 Lesser Known Tips for JavaScript Best Practices