8 Overlooked Technical SEO Issues That Impact Core Web Vitals in 2025

Your site speed tanked last month despite no content changes. Rankings dropped for seemingly no reason. Google keeps updating Core Web Vitals metrics, leaving your team scrambling to keep up. Most businesses focus exclusively on content, while technical issues silently sabotage rankings. In 2025, Google weighs technical performance more heavily than ever. Here are eight often-overlooked technical SEO issues that could be dragging down your rankings:

1. Unused JavaScript Bloating Load Times

Dead JavaScript code clogs many websites, especially those relying on pre-built themes or numerous plugins. This redundant code loads on every page, even when it’s never executed. How to fix it:

• Run Coverage reports in Chrome DevTools to identify unused code.
• Watch for red bars indicating redundant JavaScript.
• Use modern bundlers like Webpack to tree-shake unnecessary code during builds.

Replace bulky libraries with smaller, more efficient alternatives.

2. Non-Optimized Images Still Dominate Page Weight

Many sites compress large hero images but overlook smaller assets like icons, logos, backgrounds, and thumbnails. These collectively consume significant bandwidth. How to optimize:

• Use WebP format with PNG fallbacks for better compression.
• Add width and height attributes to images to prevent layout shifts during loading.
• Lazy-load below-the-fold images with the loading="lazy" attribute.

Use responsive images with srcset to serve appropriately sized images for different devices.

3. Render-Blocking CSS Penalties Increasing

Google now penalizes render-blocking resources more severely. Critical CSS should load inline, while non-critical styles should load asynchronously. Solutions:

• Split stylesheets into critical (above-the-fold) and non-critical components.
• Use media queries to prevent desktop styles from loading on mobile.

Remove unused CSS files for features your site doesn’t use (e.g., sliders, lightboxes).

4. Third-Party Scripts Causing Interaction Delays

Analytics, chat widgets, and ad scripts often trigger significant Interaction to Next Paint (INP) delays. Many developers add these scripts without considering their performance impact. How to reduce delays:

• Move non-essential scripts to load after page interaction using the defer attribute.
• Use tag managers to control script loading priority.

Implement facade patterns for heavy scripts (e.g., video embeds) by replacing them with lightweight placeholders until needed.

5. Font Loading Creating Unexpected Layout Shifts

Custom fonts often cause Cumulative Layout Shift (CLS) issues by replacing system fonts after loading. Google now measures micro-shifts more precisely. Optimization tips:

• Add font-display: swap to prevent invisible text during font loading.
• Preload critical fonts with <link rel="preload"> tags.
• Embed critical font subsets directly in CSS for faster rendering.

Self-host fonts to eliminate external DNS lookups.

6. Missing Cache-Control Headers Forcing Repeat Downloads

Without proper Cache-Control headers, browsers repeatedly download unchanged assets, slowing page load speeds. Fix this by:

• Setting max-age values based on asset update frequency.
• Using immutable flags for versioned assets that never change.
• Adding stale-while-revalidate directives to serve cached content while refreshing in the background.

Check for missing or conflicting cache headers across different assets.

7. Excessive DOM Size Slowing the Parser

Overly complex HTML structures force browsers to build and manipulate massive DOM trees, slowing down rendering. Optimization strategies:

• Simplify nested div structures.
• Watch for CSS frameworks that create unnecessary wrapper elements.
• Identify and remove excessive HTML comments or empty containers.
• Keep the DOM element count low for optimal performance, especially on mobile.

 8. HTTP/2 Multiplexing Not Properly Leveraged

While many sites use HTTP/2, they often fail to optimize asset structure to benefit from multiplexing. How to leverage HTTP/2 effectively:

• Break large bundles into smaller, logical components.
• Avoid concatenating multiple JS files into one massive bundle.
• Configure servers to prioritize critical resources.
• Remove domain sharding techniques, which were beneficial for HTTP/1.1 but hurt HTTP/2 performance.

  Final Thoughts

Detecting these technical issues requires specialized tools and expertise most teams lack internally.

At Kreative Machinez, the best SEO agency in Kolkata, our technical SEO audits specifically target hidden performance problems affecting Core Web Vitals. We don’t just identify issues—we fix them.

Many clients come to us confused about why their content investments haven’t paid off in rankings.

The answer typically lies in these overlooked technical factors.

If you want to know whether these hidden problems are affecting your site’s performance, reach out to Kreative Machinez for a detailed technical assessment that looks beyond the obvious content factors. We’ll help resolve these issues and ensure your site ranks higher on SERPs for relevant keywords.