Load Google Tag Manager script as asynchronous #121
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This pull request proposes to create the Google Tag Manager script using the
asyncattribute on thescriptelement` (see MDN reference).The DAP script appends a Google Tag Manager script to the page, but it does so without marking the script as asynchronous. This causes the script to block the main thread, impacting user-facing performance.
This reflects in performance audits of our site, which flag Google Tag Manager as blocking main thread for upward of 300ms.
Related resource: https://web.dev/articles/optimizing-content-efficiency-loading-third-party-javascript#async-defer
Google's documentation for Google Tag Manager also uses
asyncin its own default script snippet examples: