WordPress performance checks in Shadow

The largest family: caching, compression, minification, image handling, lazy loading, fonts, database tuning, and a long list of checks on the scripts and styles that load in the admin area.

There are 63 checks in this family, split into 5 pages by topic. Shadow reports what it finds, and nothing is changed until you approve a fix.

Performance checks by topic

Caching and delivery (9 checks): Whether pages are cached and delivered quickly: page and object caching, browser caching headers, compression, HTTP/2 or HTTP/3, a CDN for static files, OPcache and the PHP memory limit.
Images and fonts (9 checks): How images and web fonts are sized, compressed, lazy-loaded and served, including modern formats, responsive images and the layout shift caused by missing dimensions.
Front-end assets and head tags (20 checks): The scripts, styles and tags WordPress adds to every public page: minification, deferred JavaScript, critical CSS, emoji and embed assets, and discovery links and version tags in the page head that most sites do not need.
Admin area and plugins (13 checks): What loads in the WordPress admin and how heavy the plugin set is: blocking and inline scripts, unminified plugin assets, widgets on the dashboard, the Heartbeat API and autosave interval.
Database and cleanup (12 checks): Database tuning and tidy-up: autoloaded options, missing indexes, orphaned rows, expired transients, revision limits, storage engine and character set.

The other check families

Shadow is free and runs on your own server, with no account. The source is on GitHub, and these descriptions come from it.