068 - Stop Blaming the Theme: What's Really Killing Your Shopify Store's Speed

<p>Shopify performance specialist Izaac Barratt of Baseline Commerce joins Karl and Taylor for a deep dive into site speed optimization. </p><p>The conversation covers the full spectrum from LCP and INP fundamentals to the real-world friction of app bloat, AI coding habits, and what actually moves the needle for conversion rates. A must-listen for any theme developer, app developer, or agency working with high-traffic Shopify stores.</p><p><br></p><p><strong>Sponsor</strong></p><p>The Support Heroes - https://www.thesupportheroes.com/?utm_source=liquid_weekly&amp;utm_medium=podcast&amp;utm_campaign=sponsorships</p><p><br></p><p><strong>Subscribe to Liquid Weekly</strong></p><p>Don&#39;t miss out on expert insights and tips—subscribe to Liquid Weekly for more content like this: https://liquidweekly.com/</p><p><br></p><p><strong>Find Izaac Barratt Online</strong></p><p>LinkedIn:</p><p> https://www.linkedin.com/in/izaac-barratt — where he posts performance tips, resources, and his ongoing series on the nine performance fix buckets</p><p>Baseline Commerce:</p><p> <a href="http://baseline-commerce.com" target="_blank">baseline-commerce.com</a> — Izaac&#39;s site speed optimization consultancy</p><p><br></p><p><strong>Timestamps</strong></p><p>01:23 – Intros; welcoming guest Izaac Barrett</p><p>02:48 – Izaac&#39;s origin story: animation, Newgrounds, and e-commerce</p><p>05:36 – What drew Izaac to performance optimization</p><p>06:00 – First site speed project: 12 seconds to 2 seconds, conversion doubled</p><p>10:00 – LCP fundamentals: above-the-fold prioritization and perception</p><p>18:00 – Preloading, lazy loading, and how to get them wrong</p><p>20:43 – Liquid&#39;s preload tag, sections_index, and reducing JavaScript dependency</p><p>26:38 – Telling AI to prioritize HTML/Liquid and CSS over JavaScript</p><p>31:01 – Async vs. defer vs. render-blocking scripts explained</p><p>35:28 – Apps and performance: identifying problem apps, merchant conversations</p><p>39:15 – Advice for app developers on loading strategy and user interaction cycles</p><p>41:42 – INP (Interaction to Next Paint) explained: what it is and why it&#39;s hard to fix</p><p>43:30 – Shopify/research report: 34ms of INP = 3.5% drop in CVR</p><p>46:06 – How to debug INP: Chrome DevTools performance tab and CrUX data</p><p>53:20 – Izaac&#39;s LinkedIn series: nine buckets of performance fixes</p><p>56:17 – Dev Changelog</p><p>1:02:44 – Picks of the Week</p><p><br></p><p><strong>Dev Changelog</strong></p><p>- Next-Generation Events — Developer Preview: https://shopify.dev/changelog</p><p>- ⚠️ Expiring Offline Access Tokens Required for All Public Apps — January 1, 2027: https://shopify.dev/changelog</p><p>- Shop Minis — March/April 2026 Update: https://shopify.dev/changelog</p><p>- Customer Account UI — Feature Preview: https://shopify.dev/changelog</p><p>- App Home as a UI Extension: https://shopify.dev/changelog- llms.txt / agents.md in Shopify Themes: https://shopify.dev/changelog</p><p><br></p><p><strong>Picks of the Week</strong></p><p>Karl:</p><p>The Dark Journey: The Tragedy of the Donner Party</p><p> by Allan Eckert – A true history of the ill-fated 1846 wagon party, written by one of Karl&#39;s favorite frontier authors; dark but compelling, especially for history enthusiasts. https://www.amazon.com/Dark-Journey-Allan-W-Eckert/dp/1931672539</p><p><br></p><p>Izaac:</p><p> Page Speed Impact Estimator <a href="http://fastersite.ai" target="_blank">fastersite.ai</a> – A tool for estimating the performance gains of removing specific scripts and assets before actually doing the work; great for benchmarking and scoping conversations with clients.</p><p><br></p><p>Taylor:</p><p>The Will of the Many</p><p> by James Islington – A sci-fi novel recommended by Taylor&#39;s brother (a bookseller); follows a teenager hiding his royal lineage in a Roman Empire-style society that literally harvests people&#39;s will to gain power. Book two also out. https://www.goodreads.com