Is your Site Speed "Good" enough, or are there still CRO opportunities?

Hey {{first_name}},

Ok, so your website isn’t “slow”… but is it a bit jumpy? Or a bit laggy? Or maybe it’s just a bit annoying?

Those are the things that annoy visitors enough so that they do not want to shop on your site.

Yesterday I promised a short guide on how to check your site speed and see if you’ve got easy wins, or if you’re already good to.

Here it is…

Google measures page speed with 3 core metrics.

LCP (Largest Contentful Paint)
This measures how long it takes from when the page starts loading until the largest piece of content above the fold (initial viewport) shows. Usually, this is an image, a video or a headline. From a user perspective, this is the key perceived-load time.

Goal: Google says 2.5s or less gets you a "Good" but from a perspective of CRO aim for less than 1.5s on mobile.
INP (Interaction to Next Paint)
This measures how long it takes from a user interaction (tap, click, key press) until the page shows the next visual update. INP looks at all interactions across a visit and reports a single number that most (or nearly all) interactions fall under, so it reflects how consistently responsive the site feels. If INP is high, users get the impression that the site is broken and start rage-clicking.

Goal: Google’s “Good” is 200ms or less. For CRO, aim for less than 150ms on mobile.
CLS (Cumulative Layout Shift)
This measures how much your page layout shifts while it loads. Think buttons moving, image sliders with different heights, delayed injection of reviews or apps injected on the page that push everything down or move the position of elements. If CLS is high, people misclick, lose their place, and trust drops. From a CRO perspective, this is very distracting and pure friction.

Goal: Google classifies 0.1 or lower as “Good,” but aiming for 0 is a feasible target and ensures your site feels rock-solid.

The 10-minute speed check

(Repeat the below for 3 templates: your homepage, a collection page and a product page.)

Step 1: Check real user speed

Go to PageSpeed Insights. Paste in your URL.

Look are real user data. If the core metrics are green, there are possibly bigger fish to fry CRO-wise, but, as mentioned, Google’s “Good” isn’t CRO's gold standard.

Step 2: Test it like a customer

Sometimes Google is wrong, so do a manual test on your phone (on mobile data, not your WiFi).

Open the site fresh in incognito (not a tab that’s been open for hours) and look for these 3 red flags as you browse:

The main content takes ages to appear
The page jumps around as things load
Taps feel delayed (you click, it thinks about it, then reacts)

Step 3: Find the easiest win

Nine times out of ten, the culprit is one of these:

Oversized images
Yes, Shopify now automatically converts images to WebP, which helps, but it does not mean your images are automatically “fully optimised”.

Think of it like vacuum-sealing a puffer jacket. It compresses better, but if you shove a massive jacket in there (a huge original image), it’s still a big lump.
Too many apps and scripts
Every app you install can add extra JavaScript and third-party requests. Even if each one is small, they stack up and slow down the first load and the rate at which the page becomes usable.

Common culprits include pop-ups, chat widgets, reviews, loyalty programs, bundles, personalisation tools, and tracking scripts.
Heavy video above the fold
Autoplay video in the hero area often becomes the largest element on the page, which can drag out load time. It can also compete with other critical files, so key content appears later, and the page feels slow, especially on mobile.
Custom or Premium Fonts
Custom fonts require separate files to be loaded for rendering. This can make text appear late, swap after load, or cause the page to jump as the font loads. Even if the site is technically loading, this movement makes it feel unstable and less polished.
Theme bloat
If a theme has been edited and “improved” over time, it often ends up loading extra CSS, JavaScript, unused sections, and leftover app code. You might not see it on the page, but the browser still has to download and process it, which adds weight and slows everything down.