How can I improve my page speed in Webflow, specifically regarding render-blocking resources and unused JS? My site's mobile speed is slow due to Webflow sending one large JS file instead of splitting it into smaller packages.

Improving page speed is crucial for providing a great user experience and optimizing your website for search engine rankings. In the specific case of Webflow, addressing render-blocking resources and optimizing unused JavaScript can significantly improve your site's mobile speed.

To begin, let's tackle the issue of render-blocking resources. Render-blocking resources are files (e.g., CSS or JavaScript) that prevent the browser from rendering the webpage until they are completely loaded. These resources often slow down page speed and hinder the user experience. Here are a few strategies to minimize the impact of render-blocking resources:

1. Inline Critical CSS: Critical CSS refers to the CSS required to render the above-the-fold content of your webpage. By inline (or embedding) this CSS directly into the HTML, you reduce the number of external CSS files and eliminate render-blocking CSS. You can use tools like Webflow's built-in Critical CSS Generator or third-party services like CriticalCSS to generate and include critical CSS.

2. Optimize CSS Delivery: To prevent render-blocking CSS, you can load non-critical CSS asynchronously or delay its loading until the critical content is displayed. By doing so, the browser can render the page without waiting for the entire CSS file to load. Webflow's conditional loading feature allows you to prioritize specific CSS for different devices or breakpoints, enhancing mobile speed.

Now let's focus on the issue of unused JavaScript. Sending one large JavaScript file can increase load times, particularly on mobile devices with limited processing power. To optimize unused JavaScript, consider the following approaches:

1. Remove Unused JavaScript: Review your website's JavaScript files and remove any code that is unnecessary or no longer in use. Unused JavaScript adds to the file size and increases loading time. Webflow's JavaScript editor lets you easily identify and eliminate redundant code.

2. Split JavaScript into Modules: Instead of sending a single large JavaScript file, consider splitting it into smaller modular files. Splitting the code allows the browser to fetch only the necessary modules, avoiding unnecessary resource loading. Webflow's Asset Manager enables you to upload and manage multiple JavaScript files, allowing you to split your codebase effectively.

3. Deferred and Asynchronous Script Loading: Use the async or defer attributes when including external JavaScript files in your HTML. The async attribute loads the script asynchronously, parallelizing its loading with other resources, while the defer attribute loads the script after the HTML is parsed, ensuring it doesn't block rendering. Utilizing these attributes can speed up page rendering and enhance the performance of your site.

4. Code Optimization: Review your JavaScript code to identify areas for optimization. Techniques like minification and compression can reduce file sizes and improve loading times. Online tools like UglifyJS and Babel minify can help you compress your JavaScript code.

By implementing these strategies, you can significantly improve page speed by addressing render-blocking resources and optimizing unused JavaScript. It's important to periodically test your website's performance using tools like Google PageSpeed Insights or WebPageTest to track improvements and identify any areas for further enhancement.