Troubleshooting common issues with Optimize LCP Images within Jetpack Boost

If Jetpack Boost isn’t optimizing your Largest Contentful Paint (LCP) images as expected, this guide can help you identify common issues and resolve them.

Pages not being optimized

Check page availability

• Ensure your important pages are publicly available, and not password protected.
• Verify pages return 2XX HTTP response (not 404 or server errors).

Review page structure

• Pages with one clear, prominent visual element work best.
• Multiple competing large images can complicate LCP detection.
• Very complex layouts may require manual optimization.

Optimization results not visible

Clear caches

• Clear your site’s page cache.
• Clear CDN cache if applicable.
• Test in a private/incognito browser window.

Verify implementation

On a Cornerstone Page, view the page source and look for the following attributes:

• fetchpriority="high" on optimized images.
• loading="eager" instead of lazy loading.
• data-jp-lcp-optimized="true"

Specific error types

HttpError

Cause:

The page failed to fully load within 60 seconds — often due to slow server response or large, complex pages.

Solution:

• Check your hosting performance and server logs.
• Make sure the page loads quickly and reliably.
• Try testing with a lighter version of the page.

LcpTimeout

Cause:

Jetpack Boost couldn’t reach the page due to a network or HTTP error — usually caused by timeouts, firewalls, or unstable connections.

Solution:

• Verify the page loads consistently and returns a valid response (2XX HTTP code).
• Ensure your hosting provider allows external services like Jetpack to access your site.
• Temporarily disable security or firewall rules that may block Jetpack.

LcpMetricTimeoutError

Cause:

Jetpack Boost loaded the page successfully, but couldn’t detect the Largest Contentful Paint element within 60 seconds.
This can be caused by pages with slow-loading content, or dynamic content that never stabilizes.

Solution:

• Ensure the page has visual content that loads within a reasonable timeframe.
• Check for JavaScript errors or infinite loading states that prevent content from stabilizing.
• Verify the page isn’t primarily empty, redirect-heavy, or composed entirely of dynamically-loaded content.

ElementNotUnique

Cause:

Jetpack Boost detected multiple large visual elements and couldn’t determine which one should be optimized as the LCP.

Solution:

• Simplify your layout or ensure there’s one clearly dominant visual near the top of the page.
• Avoid having multiple competing hero images or background sections above the fold.

ElementNotStable

Cause:

Jetpack Boost identified a potential Largest Contentful Paint element, but it did not remain consistently visible for several seconds during analysis. This often occurs with carousels/auto‑rotating sliders, animated hero sections, or components that quickly swap, fade, or slide content after load.

Solution:

• Keep the hero/LCP element visible for at least 3 seconds during initial load (e.g., pause or delay autoplay/rotation).
• Set the slider to start on the hero slide and delay the first transition (≥ 3s).
• Minimize heavy entrance animations that immediately replace the hero content.
• If you cannot make these changes yourself (e.g., using a theme or slider plugin without settings):
  • Contact the theme/slider plugin authors and request that their carousel respects prefers-reduced-motion: reduce (pause/disable autoplay and transitions when users prefer reduced motion).
  • Ask for a setting to disable or delay autoplay on initial load so the main slide remains visible long enough for analysis.

Unknown

Cause:

Jetpack Boost was unable to determine the cause of the issue during analysis.

Solution:

• Wait a few minutes and try again.

Still Need Help?

Please contact support. We’re happy to advise.