Large network payloads cost users real money and are highly correlated with long load times. Lighthouse reports the total byte size in killobytes of all network resources in the Diagnostics section:
Understand how network payload affects performance and costs
Lighthouse sums up the total byte size of all resources that the page requested. Click View Details to see your page's requests. The largest requests are presented first.
Aim for total byte size to stay 1600 KB; The target score of 1600KB is based on what a page can theoretically download on a 3G connection, while still achieving a time-to-interactive of 10 seconds or less. See googlechrome/lighthouse/pull/1759.
An average network payload is between 4000 and 5000 KB. The audit fails, once your network payload exceeds 5000 KB. See Highest Correlation To Load Time to view the correlation between requests and load time.
Reducing the total size of network requests speeds up page load time and saves your users money that they would have spent on cellular data. See What Does My Site Cost to calculate the cost of viewing your site around the world. You can adjust the results to factor in purchasing power.
Strategies for reducing payload size
Here are some strategies for reducing payload size:
- Defer requests until they're needed. See The PRPL Pattern for one possible approach.
- Optimize requests to be as small as possible. Possible techniques include:
- Cache requests so that the page doesn't re-download the resources on repeat visits (see The options in your caching toolbox).
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