Preloading with Solid Performance

Preloading in Solid Performance proactively builds your cache by crawling through your site’s sitemap and storing optimized URL versions before visitors request them. This makes your site feel faster to visitors and more reliable under high traffic.

Whether you’re troubleshooting slow first-time loads or trying to prepare your site after a big update, preloading helps ensure users experience your site at its fastest, even on their first visit.

What Preloading Does #

When you trigger the Preloader, Solid Performance scans your site based on the sitemap and caches each URL. Once the process is complete, any visitor who requests those pages gets a cached version served immediately, saving precious server resources and shaving seconds off load times.

Preloading also plays nicely with common workflow patterns:

• When using the Preload & Refresh All button (found under Settings > Solid Performance), your entire sitemap is re-cached in the background.
• When you purge a single page via Solid Performance > Clear Current Page in the WordPress Admin Bar, that page is automatically preloaded.
• Only one Preloader can run at a time to prevent conflicts or race conditions.
• Cache clearing is temporarily disabled while a preload job is active, so the system isn’t working against itself.

Which Cache Formats Get Created? #

Preloading builds the cache in the most efficient format your server supports. The system attempts to create one cache file per URL in the following order:

1. Gzip
2. Deflate
3. Brotli
4. Zstandard
5. HTML (uncompressed)

Once one of these formats is successfully generated for a page, Solid Performance moves on. The goal is to create the most performant file format without wasting resources.

Developers can customize the order of formats or remove formats using the solidwp/performance/preload/accept_encoding filter.

How to Use Preloading from the Command Line #

If you prefer working via WP-CLI, Solid Performance includes commands for managing the Preloader:

Check if a preload is running:

wp solid perf preload

Start a new preload (if one isn’t already running):

wp solid perf start

Cancel a running preload:

wp solid perf cancel

Frequently Asked Questions #

How long does Preloading take? #

There’s no fixed duration. The Preloader is designed to be fast and efficient, crawling multiple URLs in parallel. Completion time depends on:

• The number of URLs in your sitemap
• How fast uncached pages load
• The capacity and speed of your server

High-powered servers can finish preloading large sites in just minutes, while slower servers or very large sitemaps may take longer.

Can I add URLs that aren’t in the sitemap? #

Yes. Developers can use the solidwp/performance/preload/urls filter to manually add URLs to the preload list.

add_filter( 'solidwp/performance/preload/urls', static function( array $urls ): array {
    array_unshift(
        $urls,
        'http://example.com/my-custom-url/',
        'http://example.com/other-url/',
        'http://example.com/another-url/'
    );
    return $urls;
}, 10, 1 );

This is useful for dynamic pages or any URLs not included in your sitemap.

Can I slow the Preloader down if needed? #

Yes. If your server becomes sluggish while preloading, you can limit the CPU usage by adjusting the maximum load per core using this filter:

/**
 * Set the max load per CPU core before preloading slows down.
 * Lower values = lighter footprint.
 */
add_filter( 'solidwp/performance/preload/max_load_per_core', static fn(): float => 0.1, 10, 0 );

Use these guidelines when setting the value:

• 0.0–0.7 per core: Light load, safe range
• 0.7–1.0 per core: High load, manageable
• 1.0+ per core: Likely to cause CPU bottlenecks; throttling is triggered

This gives you control over how aggressively the Preloader runs, making it ideal for shared hosting or servers with limited resources.

Summary #

The Preloader in Solid Performance ensures your site is always ready to serve fast, cached pages—even on the first visit. It automatically detects the best cache format your server supports, provides developer customization options, and integrates seamlessly with the dashboard and WP-CLI.

Have questions or run into issues? Don’t hesitate to contact support!