Large network payloads are highly correlated with long load times. They also cost users money; for example, users may have to pay for more cellular data. So, reducing the total size of your page's network requests is good for your users' experience on your site and their wallets.
To see what accessing your site costs around the world, check out WebPageTest's What Does My Site Cost? You can adjust the results to factor in purchasing power.
How the Lighthouse network payload audit fails
Lighthouse shows the total size in kilobytes of all resources requested by your page. The largest requests are presented first:
Based on HTTP Archive data, the median network payload is between 1,700 and 1,900 KB. To help surface the highest payloads, Lighthouse flags pages whose total network requests exceed 5,000 KB.
See the Lighthouse performance scoring post to learn how your page's overall performance score is calculated.
How to reduce payload size
Aim to keep your total byte size below 1,600 KB. This target is based on the amount of data that can be theoretically downloaded on a 3G connection while still achieving a Time to Interactive of 10 seconds or less.
Here are some ways to keep payload size down:
- 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 Network reliability landing page to learn how caching works and how to implement it.)