WP CSS Merge

WP CSS Merge reduces compatible frontend stylesheet requests by combining local CSS files into cached bundles.

Version 2 uses a safety-first bundle engine:

• Uses WordPress’s resolved print order, including late dependency changes and already printed styles.
• Creates different bundles for different style sets instead of sharing one global file.
• Keeps external, inline, conditional, RTL, unsupported, and excluded styles unchanged. Bypasses bundling when other plugins filter stylesheet tags or URLs, preserving integrity hashes, CDN rewrites, and per-file attributes.
• Rebases relative image and font URLs to their original public locations.
• Writes cache files atomically in the current site’s uploads directory.
• Automatically serves the original stylesheets whenever bundling is unavailable or unsuccessful.
• Fingerprints the actual source contents, versions, settings, locale, URLs, and printed style combinations. Source changes are detected even when timestamps and file sizes are unchanged.
• Retains published bundles for cached pages across setting changes, updates, theme switches, and deactivation.
• Supports multisite with a separate cache location for each site.

The plugin never downloads remote CSS, contacts external services, or sends telemetry.

Because HTTP/2 and HTTP/3 reduce the cost of multiple requests, combining every stylesheet is not always faster. WP CSS Merge therefore combines only contiguous compatible styles. Source contents are read on each uncached PHP page request to verify freshness; existing bundles avoid repeated CSS transformation and writes.