Theme Speed Guide · Updated February 2026
Debut Speed Optimization — How to Make Debut Faster
Debut was Shopify's original default theme before Dawn. It's still widely used but built on older architecture with jQuery dependencies. Here's how to optimize it for maximum speed without sacrificing functionality.
Debut Theme Overview
Developer
Shopify
Price
Free
Category
Free
Default Speed
60-72
The Debut theme by Shopify is a free Shopify theme. Debut was Shopify's original default theme before Dawn. It's still widely used but built on older architecture with jQuery dependencies. Out of the box, Debut stores typically score 60-72 on Google PageSpeed Insights (mobile). That's below average and needs optimization work. The good news? With the right optimizations, you can push that score to 82-92 — a significant improvement that translates to faster load times, better SEO rankings, and higher conversion rates.
Speed Score: Before vs After Optimization
Default (Unoptimized)
60-72
PageSpeed Mobile Score
After Optimization
82-92
PageSpeed Mobile Score
These scores represent typical ranges we see across Debut stores. Your actual score depends on your specific configuration: how many products you display, which apps you've installed, your image sizes, and how many theme sections you use. A store with 5 installed apps will always be slower than one with 2 — regardless of theme choice.
Important context: Shopify's platform itself adds a baseline of JavaScript and CSS that you can't remove. This means no Shopify store will ever score a perfect 100. The scores above represent realistic, achievable targets for a well-optimized Debut store with a reasonable number of apps installed.
Common Speed Issues with Debut
Every Shopify theme has its own performance characteristics. Here are the speed issues we most commonly see on Debut stores, along with why each one matters:
Legacy jQuery dependency adding 90KB+ of render-blocking JavaScript
This is typically the largest contributor to slow Largest Contentful Paint (LCP) scores on Debut stores. LCP measures how long it takes for the main visual content to appear — and it's a Core Web Vital that directly affects your Google rankings.
Non-lazy-loaded product images on collection pages
Third-party scripts and render-blocking resources prevent the browser from displaying your page until they've downloaded and executed. This increases both First Contentful Paint (FCP) and Time to Interactive (TTI).
Render-blocking CSS from inline styles and external stylesheets
Loading too many resources eagerly (before the user scrolls to them) wastes bandwidth and competes with critical above-the-fold content for network and CPU resources.
Outdated Liquid patterns causing slower server-side rendering
Excess DOM elements and JavaScript increase the browser's rendering workload, leading to slower interaction responsiveness (measured by Interaction to Next Paint / INP).
Step-by-Step: How to Speed Up Debut
Follow these optimization steps in order — they're arranged from highest impact to lowest. Each tip is specific to the Debut theme and based on patterns we see across hundreds of Debut stores.
Consider migrating to Dawn — Debut is a legacy theme with inherent performance limitations
Compress all product images to WebP format, targeting under 150KB each
Minimize slideshow slides to 2-3 maximum — each slide loads its image eagerly
Remove any apps you're not actively using — Debut's jQuery base compounds third-party overhead
Use a CDN-hosted font or system font stack instead of Google Fonts loaded via link tags
Defer non-critical JavaScript by adding the defer attribute to custom script tags
🔍 SEO bonus: Optimizing your Debut theme's speed doesn't just improve user experience — it directly impacts your Google search rankings. Stores that pass Core Web Vitals rank higher. Speed optimization is the highest-ROI SEO investment for most Shopify stores.
The #1 Speed Factor Most Debut Store Owners Miss
Here's what most speed guides won't tell you: your theme is probably not the main reason your store is slow.
The average Shopify store has 15-25 installed apps, and each one can inject JavaScript and CSS into your storefront. Review apps, email popups, chat widgets, analytics trackers, upsell tools — they all add up. On a typical Debut store, third-party app scripts account for 60-80% of total JavaScript execution time.
You can optimize your Debut images and settings all day, but if you have a heavy review app loading 200KB of JavaScript and a chat widget initializing a WebSocket connection on every page load, your speed score will still suffer.
This is exactly why we built Thunder. Instead of generic speed tips, Thunder scans every installed app on your store, measures each one's actual speed impact, and shows you exactly what's slowing you down. Then it automatically optimizes how those scripts load — deferring non-essential ones, reducing blocking time, and prioritizing critical functionality.
⚡ Optimize Your Debut Store in 60 Seconds
Thunder automatically identifies which apps are slowing your Debut store and fixes them — no code changes required. See your speed report instantly.
Free plan available · No theme code changes · Works with Debut
Frequently Asked Questions
Why is my Debut theme slow on Shopify?
The Debut theme typically scores 60-72 on PageSpeed Insights out of the box. Common causes of slowness include legacy jquery dependency adding 90kb+ of render-blocking javascript and non-lazy-loaded product images on collection pages. However, the biggest speed killer for most Debut stores is third-party app scripts — review widgets, email popups, and analytics tools that load heavy JavaScript on every page. Optimizing images and deferring non-essential scripts can improve your score to 82-92.
What is a good speed score for a Debut Shopify store?
For a Debut store, a realistic optimized PageSpeed score is 82-92 on mobile and even higher on desktop. The default unoptimized score is typically 60-72. Don't aim for a perfect 100 — that's nearly impossible with Shopify's platform overhead and any third-party apps. A score above 80 on mobile is considered good, and anything above 90 is excellent.
How do I speed up Debut without breaking my store?
Start with safe, high-impact optimizations: compress all images to WebP format, remove unused apps, and enable lazy loading in your Debut theme settings. Avoid editing theme code directly unless you're comfortable with Liquid. A speed optimization app like Thunder can automatically defer third-party scripts and optimize loading order without touching your theme files — it's the safest way to improve speed.
Is Debut a fast Shopify theme?
Debut is a free Shopify theme that performs reasonably well out of the box, typically scoring 60-72 on mobile PageSpeed. As a Shopify-built theme, it follows modern performance practices. However, your actual speed depends heavily on your product images, installed apps, and how many sections you use. With optimization, Debut stores can reach 82-92.
Other Shopify Theme Speed Guides
Score: 75-85 → 90-98
Impulse Speed Guide →Score: 45-58 → 72-85
Prestige Speed Guide →Score: 42-55 → 70-83
Warehouse Speed Guide →Score: 48-60 → 73-86
Turbo Speed Guide →Score: 50-65 → 75-88
Refresh Speed Guide →Score: 70-80 → 88-96