Start with your real visitors
Open PageSpeed Insights, type your address and read the top section first. If enough people visit your site in Chrome, Google shows how fast the page really appeared for them over the last 28 days. Below it is a test on one simulated phone over a slow connection, which is good for finding causes and often slower than what your visitors see.
The gap can be large. When I tested my check on a panel of local business sites, Google had real-visitor data for the page itself on 10 of them. The simulated phone took 4.4 to 20.8 seconds to show the main content, while three visits in four saw it within 2.4 seconds on nine of those sites and within 3.1 seconds on the tenth. The note on that panel has the details.
The three numbers Google grades
Google grades how quickly the main content appears, good at 2.5 seconds or less, how quickly the page answers a tap, good at 200 milliseconds or less, and how much the page jumps while it loads, good at 0.1 or less on its own scale. It counts the visit at the 75th percentile, so three visits in four have to make the mark.
Google says its ranking systems use these numbers, and also that it shows the most relevant page even when its experience is poor. So speed decides less about where you rank than what your pages say. It matters most to a customer on a weak signal or an older phone.
What usually makes a page slow
I ran my check on 195 business websites in Los Gatos and Campbell, and the main content was slow on Google's simulated phone on 111 of them. When it is, the check names what Google's own run found. These are the usual causes:
- A large picture at the top, sent much bigger than a phone screen needs.
- A slow server, where the host takes a long time to start sending the page. A page cache or a faster host helps.
- The main picture set to load lazily, so the browser fetches it late.
- Fonts and scripts that hold the page back until they arrive.
- Widgets from other companies, such as chat, analytics and embedded maps, that run before the page can answer a tap.
What to ask your designer
- What does PageSpeed Insights show for real visitors, and what for the simulated phone?
- What is the largest thing at the top of the home page, and how big is the file?
- Does the main picture load first, or is it set to load lazily?
- Which outside scripts load before anyone taps anything, and do we need each one?
- Does the host keep a cached copy of each page, or build it again for every visit?
Check yours in half a minute
The free speed check runs Google's test, reads its real-visitor data where Google has it, and names the first thing to fix. The sites I build are plain pages that load fast on a phone, with no plugins to keep patched.