Reduce the impact of third-party code  |  Lighthouse  |  Chrome for Developers
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Reduce the impact of third-party code
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Warning: This audit has moved into the Use efficient cache lifetimes insight as of Lighthouse 13. For more information see What's new in Lighthouse 13.
To add an advertising network, social media button, A/B test, or analytics service to your page,
you usually need to add a third-party script to your HTML. These third-party scripts can significantly affect your page load performance.
How the Lighthouse audit for third-party code fails
Lighthouse flags pages that have third-party code that blocks the main thread for 250 ms or
longer:
A third-party script is any script hosted on a domain that's different to the domain of the URL
that you audited with Lighthouse. As the page loads, Lighthouse calculates how long each of the
third-party scripts blocks the main thread. If the total blocking time is greater than 250 ms
the audit fails.
How to reduce the impact of third-party code
See Identify slow third-party scripts to learn how to use
Chrome DevTools and other Lighthouse audits to detect problematic third-party code, and
see Efficiently load third-party JavaScript for
optimization strategies.
Resources
Source code for Reduce the impact of third-party code audit
Loading Third-party JavaScript
Except as otherwise noted, the content of this page is licensed under the Creative Commons Attribution 4.0 License, and code samples are licensed under the Apache 2.0 License. For details, see the Google Developers Site Policies. Java is a registered trademark of Oracle and/or its affiliates.
Last updated 2019-05-02 UTC.
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