More than half of popular homepages we checked load a render-blocking script in <head>

In Status Is UP’s October 2026 readiness snapshot, we looked at the external scripts in each homepage’s <head>. On 56% of 144,474 measured homepages, at least one of them had no async or defer attribute and was not a module script. Among the top 1,000 sites in the Chrome UX Report list that we could measure, the figure was 45%.

A classic script without those attributes is fetched and run before the browser carries on parsing the rest of the page, which can hold back the first render. MDN documents defer as running a script after the document has been parsed, and async as fetching it in parallel with parsing and running it as soon as it is available. Chrome’s Lighthouse reports scripts like these as render-blocking resources.

In many cases the fix is one attribute, but order matters: deferred scripts keep their document order, async scripts do not. An independent analytics or tag snippet is usually a good async candidate; scripts that other code depends on suit defer. This is a single dated check of each homepage’s HTML, not a speed measurement.

Each fact is checked against the primary sources listed. Spotted an error? Email the Status Is UP team. Status Is UP helps owners improve their sites; it is not an uptime monitor. For live outage status, see Status Is Down.