This is nothing new, Google told us almost a decade ago that they use site speed in their search rankings:
"Speeding up websites is important — not just to site owners, but to all Internet users. Faster sites create happy users and we've seen in our internal studies that when a site responds slowly, visitors spend less time there."
And there's about a million studies online about improving engagement/conversion with improved page speed:
As development techniques have advanced, and website owners are trying to do more with their websites, page speed has become an ever more important factor.
There are lots of different ways to optimize the delivery of content from a performance perspective, but they can roughly be split into these broad techniques:
- Optimizing the cricital path
- Optimizing images and image delivery
- Removing duplicate page resources
- Setting suitable cache headers on page resources
- Optimizing webfonts
Page Speed Issues
Most of the Page Speed Hints are Issues, which means they represent errors or problems that need to be fixed. When dealing with Page Speed 'issues', they typically relate to speed gains which can result from fixing the issue in question. They are additionally classified in terms of their importance - this should be taken into account when prioritizing implementation work, along with the number and type of URLs affected.
These Hints are very important, and definitely warrant attention.
- Resources that do not specify long cache headers
- Critical (Above-the-fold) CSS was not found
- Loads oversized images which are scaled in the browser
- Uncompressed text content resources
- Total combined image content size is too big (over 1MB)
- Contains one or more single point of failure
- DOM width exceeds recommended 60 nodes wide
- Has an excessive number of DOM nodes (greater than 1500)
- CSS content is not minified
- URL loads in one or more identical CSS Resource
- Total combined CSS content size is too big (over 500KB)
- DOM depth exceeds recommended 32 nodes deep
- Page resource URL redirects
- Keep-alive not set on page resources that are used multiple times
- Resources that do not specify cache headers
- Static resources have private cache-control header
These Hints are worth investigating further, and may warrant further attention depending on the type and quantity of URLs affected.
- Total combined size of the webfonts used is too big (over 200KB)
- Loads in too many webfonts
- Loads offscreen images that appear below the fold
- Duplicate style sheets
- Critical (Above-the-fold) CSS was found in the <head> but not loaded early enough
- Downloaded HTML is greater the 500KB
- Style sheet is loaded in with media='print'
- Loads hidden images
- Server response too slow with a Time-to-First-Byte greater than 600ms
- Loads overweighted Webfonts
These Hints are of the lowest significance, and should only be addressed if there aren't more serious issues which have not been handled.
- HTML content is not minified
- Character set is not UTF-8
- Character set not specified in <head> or headers
- Meta charset is not the first element in <head>
- Character set missing from the HTTP headers
- Contains DOM elements with empty src or href attributes
Page Speed Potential Issues
Hints marked 'Potential Issue' describe a situation that might be an issue, or might cause an issue. In the case of Page Speed Hints, they typically highlight patterns which are worth investigating, as there may be an underlying issue there which needs exploring further.
Page Speed Opportunities
Hints marked 'Opportunity' describe where you could optimize the site to potentially improve performance further.