Speed Optimizer (SG Optimizer) Review: SiteGround's Free Caching Plugin (2026)

What Is Speed Optimizer?

Speed Optimizer (formerly SG Optimizer) is a free WordPress performance plugin by SiteGround. Combines caching, minification, image compression, and database cleanup. Available to all WordPress users since v7. 4.2/5 stars (628 reviews), 95M+ downloads.

Key Features

• File-based caching + Dynamic Cache + Memcached (SiteGround only)
• Image compression — Up to 85% reduction, WebP on SiteGround
• CSS/JS/HTML minification
• Defer render-blocking JS
• Lazy loading
• Database optimization — Weekly scheduled cleanup
• Heartbeat control

Free vs Premium

100% free. SiteGround customers get exclusive: Dynamic Cache, Memcached, auto WebP, auto cache purging. Other hosts get file-based caching and standard optimizations.

Pros and Cons

Pros: Free, all-in-one, excellent on SiteGround, built-in speed test, actively maintained

Cons: 4.2 rating lower than competitors, best features SiteGround-only, no critical CSS, less configurable

Who Should Use It?

SiteGround customers — absolutely. Others — WP Rocket or LiteSpeed Cache are better options.

Best Alternatives

• WP Rocket ($59/yr) — Premium standard
• LiteSpeed Cache — Best free on LiteSpeed servers
• W3 Total Cache — Most configurable free option

Frequently Asked Questions

Works on non-SiteGround?

Yes since v7, but best features are SiteGround-exclusive.

Can I use with WP Rocket?

Not recommended — caching conflicts. Choose one.

Does it improve Core Web Vitals?

Yes. Users report 95+ PageSpeed scores on SiteGround with proper config.

How does it compare to WP Rocket?

WP Rocket is more polished overall. Speed Optimizer wins on SiteGround value (free vs $59/yr).

Sources: WordPress.org, SiteGround