Deferring third-party scripts: Crawl Audit check 99

Short answer: analytics, chat widgets, ad tags and embeds are code from other companies running on your page. Loaded the plain way, each one can hold your page up. Check 99 passes when at least 70% of the external scripts in your HTML have defer, async or type="module".

What Crawl Audit checks

• Crawl Audit counts every <script src> in the HTML, yours and third parties', and how many have defer, async or type="module".
• Pass: no external scripts, or 70% or more deferred. Warning: fewer, shown as a count.

The 70% line is Crawl Audit's own. Scripts added later by other scripts, such as a tag manager's tags or Next.js scripts loaded after the page starts, aren't in the HTML, so they aren't counted.

What Google says

• web.dev: "Because synchronous scripts delay DOM construction and rendering, you should always load third-party scripts asynchronously unless the script has to run before the page can be rendered."
• "Scripts with async can still block HTML parsing." They run the moment they arrive.
• "Use defer for less critical resources, such as a video player that's below the fold."

On devmarde.com

On 3 October our homepage had 15 external scripts in its HTML, and 14 had async or defer, so it passes.

How to fix it

• Add async to independent tags such as analytics, and defer where order matters (check 87).
• Remove tags you no longer use. Every third party adds weight (check 85).
• Load widgets such as chat or video only when the visitor needs them.

On your platform

• Next.js: next/script has three main strategies: beforeInteractive, afterInteractive (the default) and lazyOnload ("Load during browser idle time").
• WordPress: some performance plugins can add defer to scripts. Test forms and checkout afterwards.
• Shopify, Wix and Squarespace: check scripts pasted into header code injection, and apps you've installed.

Sources

• web.dev, Efficiently load third-party JavaScript, checked 3 October 2026.
• Next.js, Script component.