Before/After Shopify Speed Optimization — Case Study

Checklists are great, but nothing hits as hard as seeing a real "before/after" from a store that looks a lot like yours. That's exactly what this case study is: a behind-the-scenes look at how a slow, app-heavy Shopify store went through a structured optimization and came out fast, stable, and far more profitable.

For privacy, we'll call the client Brightlane Living — a DTC brand selling mid-range home & lifestyle products in the US, UK, and EU. Their brand was strong, creative assets were on point, and ad accounts were well managed. But performance data was telling a different story.

Use this case study alongside our more "evergreen" resources:

• How to Fix a Slow Shopify Store — Full Checklist (2025)
• Shopify Core Web Vitals: Why Your Store Is Slowing Down & How to Fix It
• Shopify Speed Optimization Guide (2025)

1. Store background & performance problems

Brightlane Living had grown quickly over the previous two years. They were running Meta, TikTok and Google campaigns at decent scale, with a healthy AOV and repeat purchase rate. Still, the marketing team felt like they were "pushing uphill":

• Prospects warmed up by ads dropped off once they hit the product page.
• Campaigns that used to work well suddenly needed steeper discounts to convert.
• Google Search Console started surfacing "Poor URL" and "Needs improvement" Core Web Vitals warnings on key templates.

Internally, the team admitted that the storefront had become a bit of a "Frankenstein":

• More than 20 apps installed, including multiple pop-up, review and upsell tools.
• Custom sections layered on top of an older, non-OS 2.0 theme.
• Legacy scripts from previous agencies left inside theme.liquid.
• Large, uncompressed images and a rotating homepage hero slider on mobile.

They had tried a couple of "one-click" speed apps, but nothing moved the needle on real-world performance. That's when they decided to invest in a full Shopify speed optimization service instead of experimenting with random settings.

2. Baseline metrics and Core Web Vitals

Every FASTRANK project starts from data. We audited three high-impact templates: the homepage, a hero product page, and a best-selling collection page. We collected both lab metrics (PageSpeed/Lighthouse) and field metrics where available.

Baseline mobile metrics (hero product page):

• PageSpeed Insights mobile score: 38/100
• Largest Contentful Paint (LCP): 5.4s
• Cumulative Layout Shift (CLS): 0.19
• Interaction to Next Paint (INP): 360ms

From the analytics side, the team shared:

• Mobile conversion rate down from 3.0% to 2.2% over 12 months.
• Checkout initiation looked strong, but add-to-cart → purchase drop-offs had increased.
• Meta's "landing page experience" signal repeatedly flagged as "Average" or "Below average".

With this baseline in place, we plugged Brightlane into our Shopify-specific optimization flow — the same one we outline in our slow store checklist and in the Shopify speed guide.

3. Step 1 — App & script cleanup

The biggest red flag in the audit was app bloat. Many of the "nice-to-have" tools were quietly loading JavaScript and CSS on every page, even when a feature only appeared in one or two places.

• Uninstalled 7 unused apps: an old spin-to-win wheel, two overlapping announcement bar tools, a legacy chat widget and several campaign-specific apps.
• Consolidated pop-ups: moved from three different pop-up/email capture apps to a single, leaner solution.
• Streamlined social proof: replaced two review/UGC widgets with one app configured to load only where it actually added value.
• Cleaned legacy scripts: on a cloned theme, we removed leftover script tags and snippets injected by previous agencies and uninstalled apps.

That first pass reduced the number of network requests on the product page by ~30% and trimmed total JavaScript payload by just over a third.

4. Step 2 — Theme & layout optimization

Once the noisiest scripts were gone, we turned to the theme. The goal here wasn't a full redesign, but a structural tidy-up so the browser could reach the important content as quickly and predictably as possible.

• Prioritized above-the-fold content: made sure the main product image and primary title/price block were early in the HTML and not wrapped in unnecessary containers.
• Removed heavy sliders on mobile: swapped a large autoplay hero carousel for a single, compressed hero image on small screens.
• Reserved layout space: added explicit height for the header, announcement bar and primary media to reduce layout jumps and CLS.
• Simplified mobile sections: collapsed some "nice but not critical" home sections for mobile, focusing above-the-fold real estate on value props and key products.

None of these changes altered the core brand look and feel, but they drastically reduced the amount of layout work the browser had to perform before the shopper could interact.

5. Step 3 — Image & media fixes

The next major bottleneck: imagery. Product photography looked great, but assets were often 1–3MB each and uploaded at much larger dimensions than needed.

• Compressed key hero assets: brought homepage and top product hero images down to ~180–220KB using modern compression.
• Introduced WebP where possible: served WebP versions to compatible browsers with JPEG/PNG fallback for older ones.
• Standardized collection thumbnails: normalized image ratios across cards, improving both aesthetics and layout stability.
• Enabled lazy loading: deferred lower-page lifestyle shots, reviews images and secondary gallery photos until the user scrolled near them.

After this phase, the primary LCP element on the product page consistently loaded far earlier, even on 4G connections.

6. Step 4 — Core Web Vitals tuning

With apps, theme structure and media under control, we moved into more precise Shopify performance optimization centered around Core Web Vitals: LCP, CLS and INP.

• Deferred non-critical scripts: moved multiple marketing pixels, chat widgets and survey scripts to load after the first paint or after user interaction.
• Optimized fonts: reduced the number of font weights, self-hosted key fonts and used font-display strategies to avoid invisible text flashes.
• Reduced main-thread work: refactored custom variant-switching logic and removed unused code paths that were blocking interaction.
• Configured smarter caching/CDN rules: leaned on Shopify's infrastructure plus CDN configuration to improve repeat-visit and international performance.

At the same time, we set up monitoring so Brightlane could see how Core Web Vitals evolved for real users over time, not just in one-off lab tests.

7. Before/after results (scores & revenue)

After deploying the optimized theme, we let things run for a few weeks to gather meaningful data and then compared the results against the baseline.

Updated mobile metrics (hero product page):

• PageSpeed Insights mobile score: 38 → 92
• Largest Contentful Paint (LCP): 5.4s → 2.0s
• Cumulative Layout Shift (CLS): 0.19 → 0.04
• Interaction to Next Paint (INP): 360ms → 110ms

Business impact over the next 8–10 weeks:

• Mobile conversion rate increased by 24% compared to the previous period.
• Average order value remained stable — the gains came from better conversion, not deeper discounting.
• Meta and Google reported improved landing page experience scores and more stable ROAS.
• Support tickets about "site feels slow" or "page didn't load" dropped significantly.

The most important feedback came from the client's own team: "The store finally feels instant again, even on older phones." Product pages opened smoothly, and elements stayed where shoppers expected them.

8. Key lessons for other Shopify merchants

Brightlane's situation isn't rare. If you've been scaling your Shopify store for a while, there's a good chance you recognise some of these patterns. Here are the biggest takeaways you can apply right away:

• Speed problems are usually layered, not caused by one thing. It's rarely a single "bad" app or image. It's years of small decisions that add up.
• Core Web Vitals respond well to a clear process. When you follow a structured checklist instead of random tweaks, improvements are more predictable and safer.
• You don't always need a new theme. In this project we optimized around the existing theme instead of starting from zero.
• Guardrails matter after the fix. Once the store was fast, we helped them put in rules so new apps, scripts and sections couldn't silently undo the work.

If you're just starting, work through the flow in our slow-store checklist, then dive deeper into the metric side with the Shopify Core Web Vitals guide.

9. How to get similar results with FASTRANK

You can absolutely replicate many of the changes from this case study on your own — especially app inventory, basic image work and a first pass at layout cleanup. But if your store is a meaningful revenue channel, or your team simply doesn't have the time to iterate for weeks, working with specialists is often the smarter play.

At FASTRANK, our improve Shopify speed service follows a repeatable, transparent process:

• Deep audit of your theme, apps, scripts and Core Web Vitals.
• Prioritized action plan focused on real user experience and revenue, not just lab scores.
• Implementation on a staging theme with backups, QA and safe deployment.
• Clear before/after reporting you can share with stakeholders or clients.

If you'd like your own "before/after" chart that looks like Brightlane's, you can explore our Shopify optimization offers here: See Shopify speed optimization plans ?

And if you also run a content hub on WordPress, our WordPress Speed Optimization Guide (2025) shows how we apply the same Core Web Vitals mindset on the publishing side of your stack.