Why Your PageSpeed Insights Score Doesn't Improve Overnight (Even After Making Changes)

We know how frustrating it can be: you follow Google PageSpeed Insights recommendations, apply our support team’s tips, and… your score still doesn’t budge.

Before you think all that effort was wasted — here’s the truth: you are improving your store, but PageSpeed Insights needs time to show it.

Let’s break down the why.

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1. Lab Data vs. Field Data — The Two Sides of PageSpeed Insights

When you perform an analysis in PageSpeed Insights, the results you’ll see are basically from two different sources:

Lab Data

• Runs in a controlled environment (like a test drive in perfect weather).
• Updates immediately when you make changes.
• Great for spotting issues and testing fixes.
• These are what you see under the “Diagnose performance issues” heading.

For example, this is when you make adjustments on images either by:

• changing their dimensions to better fit the suggestions and/or;
• changing their formats, like when moving them from .jpg to .webp.

Even though improving images can have a positive impact on performance, it’s only one part of the bigger picture. Your PageSpeed Insights score won’t necessarily jump right away — especially in Field Data, which waits for real visitors over time before reflecting improvements.

Field Data

• Based on real visitor experiences.
• Uses a 28-day rolling average — meaning it blends old data with new data for almost a month.
• Needs real-world visits to collect performance numbers.
• Appears under the heading Core Web Vitals Assessment.

In short: Lab data = instant; Field data = takes weeks.

Think of it like going to the gym: you won’t see results after just one day of working out.

• Lab Data is like stepping on the scale right after your workout — you might notice a quick change because you lost some water weight.
• Field Data is like tracking your progress over a month — it reveals the real, lasting improvements in your fitness.

But here’s a reality check: PageSpeed Insights is not an exam where only 100/100 means success.
What matters is how your store compares to competitors.

Even Amazon.com, one of the most optimized ecommerce sites in the world, can sometimes show “red” results in PageSpeed Insights. The key question is: if your competitor’s product page loads slower than yours, who provides the better experience? You do.

What is a competitor?

In ecommerce, your competitors are not always the big global brands. They are the stores where your potential customers might go instead of yours.

• If you sell sneakers, your competitors are other online sneakers stores targeting your market (not necessarily Nike).
• If you sell handmade crafts, your competitors might be local Etsy sellers or small Instagram shops.
• Sometimes, competitors are indirect: for example, if you sell gym equipment, even a fitness app can compete for the same customer’s money.

How to study competitors with PageSpeed Insights

1. Identify 2–3 real competitors (search Google for your main product + “buy online” and see who appears).
2. Run their homepage and one or two key product pages in PageSpeed Insights.
3. Look at their Field Data metrics (Largest Contentful Paint, First Input Delay, CLS).
4. Compare their results to yours.
5. Aim to be consistently faster and smoother than them — not to eliminate every single warning or reach a perfect score.

Pro Tip: Being even slightly better than the competition can improve conversions. Customers rarely notice a perfect score, but they do notice when your site feels quicker and easier than the one they just left.

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2. Why Results Take Time to Show Up

Field data doesn’t refresh instantly because it’s built to represent average real-world performance. If you improved your store today, visitors tomorrow will start experiencing those benefits — but the metrics still include the last 28 days of “previous” data.

Next you can find an example timeline:

• Day 0: You make improvements
• Week 1: Slight improvement if you have high traffic
• Week 4: Full improvement visible in your metrics

So the lower your traffic is, the longer it takes to replace old data with new data.

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3. Common PageSpeed Insights Suggestions (Explained Simply)

Here are some examples of what you might see in PageSpeed Insights, what they mean, and why the changes you make take time to show up in your score.

Use Modern Image Formats (WebP, AVIF)

PageSpeed might say: “Serve images in next-gen formats”

• What it means: Your current images are heavier (JPG, PNG) and could load faster if saved in newer formats like WebP or AVIF.
• Real-life analogy: Like swapping an old bulky suitcase for a lightweight one — it’s easier to carry (load) for your visitors.
• Why the score doesn’t change instantly: Even after converting images, the field data still contains performance from before the change until the 28-day average catches up.

Note: You can read more about the use of images in Jumpseller Themes in this article.

Reduce Layout Shift (CLS)

PageSpeed might say: “Avoid large layout shifts”

• What it means: Elements on your page (like banners or product images) move around after loading, causing the layout to “jump” unexpectedly.
• Real-life analogy: Imagine reading a magazine and the text suddenly shifts, making you lose your place — it’s frustrating for visitors.
• Why the score doesn’t change instantly: Improvements only register after real visitors experience the smoother layout over enough days to replace old data.

Eliminate Render-Blocking Resources

PageSpeed might say: “Remove unused CSS/JS” or “Eliminate render-blocking resources”

• What it means: Your site is loading scripts (e.g. javascript files) and styles (e.g. CSS files) that slow down the first paint (when visitors first see something on the screen).
• Real-life analogy: Like unpacking every box from a moving truck before letting guests in — you could let them in sooner, while still unpacking in the background.
• Why the score doesn’t change instantly: Even if you optimize these scripts today, old data still affects the rolling average for weeks.

Serve Static Assets Efficiently (Caching)

PageSpeed might say: “Serve static assets with an efficient cache policy”

• What it means: Files like images, CSS, and JS aren’t being saved (cached) in visitors’ browsers for long enough, forcing them to re-download every time.
• Real-life analogy: Imagine re-printing a restaurant menu for every customer instead of letting them reuse the same one.
• Why the score doesn’t change instantly: Visitors who load the site after caching changes will benefit immediately, but the field data updates gradually.

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4. How to Measure Progress While You Wait

Don’t rely solely on the PageSpeed score to judge improvements. You can also track:

• Bounce rate in analytics: should go down if site feels faster.
• Time on site: should go up if customers stay engaged.
• Conversion rate: should improve with better user experience.
• Real live experience: if you have a decent and trustworthy internet connection and your store loads fast, it’s already a good sign.

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5. Final Takeaway

Your efforts are not wasted — they just need time to be reflected in the public score. Field data is like a moving average: the old performance is slowly replaced by the new.

Keep optimizing, keep monitoring, and remember: the real goal isn’t just a perfect score — it’s a store that feels fast and smooth for your customers.