Performance
Core Web Vitals and what slows a page down.
- infoCaching DisabledCache-Control turns caching off for a public response
- moderateCLS Needs ImprovementCumulative Layout Shift is over 0.1
- seriousContent Wider Than Mobile ViewportElements with fixed widths can cause horizontal scrolling on mobile
- minorImages Not Lazy LoadedBelow-fold images should use lazy loading
- moderateImages Without DimensionsImages missing width/height attributes cause layout shifts
- moderateLarge CSS PayloadTotal CSS size is too large
- moderateLarge DOM SizePage has too many DOM elements
- moderateLarge HTML DocumentHTML document is too large
- moderateLarge Images Without Mobile OptimizationImages over 200KB without srcset serve desktop-sized images to mobile devices
- moderateLarge Inline ScriptsInline scripts are too large to cache or compress well
- moderateLarge Inline StylesInline styles are too large to cache well
- moderateLarge JavaScript PayloadTotal JavaScript size is too large
- moderateLarge Page SizeTotal page size is too large
- moderateLCP Needs ImprovementLargest Contentful Paint is over 2.5 s
- moderateMissing Cache HeadersResponse lacks proper cache control headers
- minorMissing Cache ValidationResponse lacks ETag and Last-Modified headers
- minorMissing font-display: swapWeb fonts may cause invisible text during loading
- moderateMissing Response CompressionResponse is not compressed with gzip or brotli
- minorMissing Responsive ImagesImages lack srcset for responsive delivery
- minorNot Using HTTP/2Server is not using HTTP/2 protocol
- seriousPoor CLS (Cumulative Layout Shift)Cumulative Layout Shift is over 0.25
- seriousPoor LCP (Largest Contentful Paint)Largest Contentful Paint is over 4 s
- minorPotential 300ms Tap DelayWithout touch-action or proper viewport, touch interactions have a 300ms delay
- moderateRender-Blocking CSSCSS files in head block first paint
- moderateRender-Blocking ScriptsScripts in head without async/defer block rendering
- seriousSlow Server ResponseServer took too long to respond
- moderateSmall Base Font Size for MobileBody font size below 16px causes iOS to zoom in on form inputs
- moderateToo Many HTTP RequestsPage makes too many HTTP requests
- moderateToo Many JavaScript FilesPage loads too many script files
- minorToo Many StylesheetsPage loads too many CSS files
- minorToo Many Web FontsPage loads too many web fonts
- seriousTotal Image Payload Too LargeImages add up to too much data
- moderateUnoptimized ImagesLarge images that could be optimized
- moderateUses document.write()document.write() can delay page load
- seriousViewport Meta Missing device-widthThe viewport meta tag doesn't set width=device-width