“Measuring TTFB remotely means you’re also measuring the network latency at the same time which obscures the thing TTFB is actually measuring: how fast the web server is able to respond to a request.
The TTFB being reported is not the time of the first data byte of the page, but the first byte of the HTTP response. These are very different things because the response headers can be generated very quickly, but it’s the data that will affect the most important metric of all: how fast the user gets to see the page.”1
Today, I was asked to “take a quick look at [a client site] and determine if there are any potential speed issues that need to be resolved,” as the “client is most concerned with load time and optimizing in that area.”
This is a screen shot of the client’s page speed report, from GTmetrix. Pictures speak a thousand words, and this one does not look good. It’s easy to empathize with the client’s concern, and I’m sure they were shown this report, or one generated on PageSpeed Insights.
But these two reports are easy for anyone, likes a salesperson, to produce and present to a prospect, even if this same salesperson is no more qualified to discuss browser caching or gzip compression than the client they are attempting to woo. At a growing agency in Utah, our sales team loved these – a visual mechanism to sow discontent.
With this in mind, I throttled a mobile page load to the low range of Verizon’s 4G network speeds in Developer tools. Above the fold content painted in less than two seconds, and the DOM fully loaded in less than 4. The page speed report may look bad, but as far as a User is concerned, the page loads fast. And this is why page speed reports should be taken with a grain of salt; the scores they output are from a computer’s perspective, not a human being’s.
Tomorrow, in addition to gently explaining the above, I’m going to use the client’s concern with page speed as an opportunity to pursue working with their CMS provider to migrate to HTTPS, and finally to ensure resources are delivered over HTTP/2. We’ll likely talk about security and why Google cares about it, as well as the speed benefits of sending multiple requests for data in parallel over a single connection. Funnily enough, these are two items not highlighted within the report on either of these two software. I’m looking forward to it.