Here is a collection of tools I’ve found useful.
Utilities
- Post Type Switcher plugin
- Duplicate Menu plugin
Performance
- Google PageSpeed Insights: pagespeed.web.dev
- GTmetrix: gtmetrix.com
- WebPageTest: webpagetest.org (Useful for waterfall chart and list of all loaded files)
Social
- Preview Open Graph data for any page: omgimg.co/social/preview
Images
- Convert SVG to CSS: yoksel.github.io/url-encoder
Accessibility
- Accessibility Checker plugin: equalizedigital.com/accessibility-checker
- Landmarks browser extension: matatk.agrip.org.uk/landmarks
- HeadingsMap browser extension: Chrome: chromewebstore.google.com/detail/headingsmap/flbjommegcjonpdmenkdiocclhjacmbi / Firefox: addons.mozilla.org/en-US/firefox/addon/headingsmap
Plugin development
- Check to make sure your plugin actually works with the minimum WP version it declares: https://github.com/eduardovillao/wp-since