A Primer in Web Performance
Performance matters. A slow site has serious effects on revenue, because both users and search engines dislike slowness.
The performance of your website directly impacts revenue per visitor:
- According to Google, a increase in load time from 1 second to 5 seconds causes a 90% increase in bounce rate for mobile users.
- Google also found that a mere 400 ms (0.4 seconds) delay caused a persistent drop in daily searches per user of 0.6%.
- Walmart saw up to 2% increase in their conversion rate for every second of reduced load time, and up to 1% revenue increase for every 100 ms (0.1 seconds) reduction.
- Aberdeen Group found that a one second delay decreased conversions by 7%.
- Microsoft studied performance for their Bing search engine and found that a 2 second delay reduced revenue by 4.3%, and reduced user satisfaction by 3.8%.
And has indirect effects on the amount of visitors coming to your site:
What causes bad performance?
Displaying a web page involves five steps:
- The browser connects to the server and asks for the document.
- The server generates the page and sends it to the browser.
- The browser analyses the page to see which external resources it needs. It asks the server for those external resources.
- The server sends the external resources to the browser.
- The browser combines the document and the external resources to display the web page.
The reason for slowness can usually be found in step 2, or in steps 3 to 5. Therefore, the causes for slowness can be divided into two categories:
- A slow server.
- A page with too many external resources.
Because step 2 must happen before anything else does, that's the first thing we should look at. Continue to investigating server slowness.