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Diagnosing Performance Issues

If your store feels slow after installing Looksy, this guide will help you identify and fix performance bottlenecks.

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Quick Performance Check

Before diving into troubleshooting, establish baseline metrics:

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Run Google PageSpeed Insights

  1. Visit PageSpeed Insights
  2. Test a product page URL
  3. Note your scores:
    • Performance score (target: 90+)
    • Largest Contentful Paint (target: < 2.5s)
    • First Input Delay (target: < 100ms)
    • Cumulative Layout Shift (target: < 0.1)
If your scores are in the “Good” range (green), Looksy is not causing performance issues.

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Common Performance Issues

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Issue: Page Load Time Increased

Test:
  1. Disable Looksy app temporarily
  2. Clear cache and test page speed
  3. Re-enable Looksy and test again
  4. Compare results
If speed is the same: Looksy is not causing the slowdown If speed improves: Contact [email protected] with details
Most common culprit for slow pagesCheck:
  • Are product images > 1MB? (Too large)
  • Are they high resolution but uncompressed?
Fix:
  1. Compress images with TinyPNG or Shopify’s image optimizer
  2. Use WebP format (Shopify supports this)
  3. Target file size: 100-300KB per image
  4. Resize to max 2048px width
Expected improvement: 1-3 seconds faster page load
Too many apps slow down storesCheck:
  • How many apps do you have installed? (> 20 is concerning)
  • Are there apps you’re not actively using?
Fix:
  1. Go to Shopify Admin → Apps
  2. Uninstall apps you don’t need
  3. Test page speed after each removal
  4. Keep only essential apps
Expected improvement: 0.5-2 seconds faster per app removed
Heavy themes impact speedTest:
  1. Switch to Dawn (Shopify’s free, fast theme)
  2. Test page speed
  3. If significantly faster, your theme is the issue
Fix:
  • Use a performance-optimized theme
  • Remove unused theme features
  • Hire developer to optimize custom theme

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Issue: Virtual Try-On Rendering is Slow

User’s connection affects speedTest:
  • Try on fast WiFi vs. cellular
  • Test with speedtest.net
  • Target: 10+ Mbps for smooth experience
If connection is slow:
  • Try-on will take longer (5-10 seconds vs. 15-20 seconds)
  • This is network-dependent, not Looksy’s fault
Large selfies take longer to uploadInstruct customers:
  • Use photos < 2MB
  • Don’t upload ultra-high-res images (8K phone photos)
  • Compress before uploading if possible
Expected improvement: 1-2 seconds faster upload
Rare server issuesIf try-on is consistently slow:
  1. Check Looksy status page (if available)
  2. Contact support to verify server status
  3. Try during different times of day
Note: Processing should be 15-20 seconds consistently

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Issue: Core Web Vitals Failing

What it measures: Time until largest element loadsCommon causes (not Looksy):
  • Large, unoptimized hero images
  • Slow server response time
  • Render-blocking JavaScript
Fix:
  1. Compress product images
  2. Use lazy loading for images
  3. Optimize hero/banner images
  4. Enable Shopify CDN
Looksy impact: None (button loads after LCP element)
What it measures: Time until page becomes interactiveCommon causes:
  • Too much JavaScript executing
  • Multiple apps loading synchronously
  • Heavy theme JavaScript
Fix:
  1. Remove unnecessary apps
  2. Minimize third-party scripts
  3. Use async loading for non-critical scripts
Looksy impact: < 10ms (async loading)
What it measures: Unexpected layout shiftsCommon causes:
  • Images without width/height attributes
  • Dynamic content insertion
  • Web fonts loading
Fix:
  1. Set image dimensions in HTML
  2. Reserve space for dynamic content
  3. Use font-display: swap for web fonts
Looksy impact: None (button has reserved space)

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Mobile Performance Optimization

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Issue: Slow performance on mobile devices

Serve smaller images to mobileShopify supports responsive images:
  • Automatically serves appropriate sizes
  • Verify theme uses responsive image tags
Check:
<!-- Good (responsive) -->
<img srcset="image_small.jpg 400w, image_large.jpg 800w">

<!-- Bad (fixed size) -->
<img src="image_large.jpg">
Mobile devices have less processing powerFix:
  1. Minimize app usage on mobile
  2. Disable non-essential features on mobile
  3. Use lazy loading aggressively
Browser testing isn’t enoughTest on:
  • iPhone (older models like iPhone 8)
  • Android mid-range devices
  • Both WiFi and 4G connections
Identify: Where does it slow down?

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Advanced Diagnostics

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Using Browser DevTools

Identify slow-loading resourcesSteps:
  1. Open Chrome DevTools (F12)
  2. Go to Network tab
  3. Reload page
  4. Sort by “Time” column (largest first)
  5. Identify bottlenecks
What to look for:
  • Files > 1MB (compress these)
  • Long wait times (server issues)
  • Many small requests (concatenate if possible)
See what’s blocking renderingSteps:
  1. Open Chrome DevTools (F12)
  2. Go to Performance tab
  3. Click Record
  4. Reload page
  5. Stop recording
  6. Analyze timeline
What to look for:
  • Long tasks (> 50ms)
  • JavaScript execution time
  • Layout thrashing
Comprehensive performance auditSteps:
  1. Open Chrome DevTools (F12)
  2. Go to Lighthouse tab
  3. Select “Performance”
  4. Run audit
  5. Review recommendations
Focus on:
  • Opportunities (biggest impact)
  • Diagnostics (specific issues)

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Shopify-Specific Optimizations

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Shopify Online Store Speed Report

Access:
  1. Shopify Admin → Online Store → Themes
  2. Click ”…” → View speed report
  3. Review metrics and comparisons
What it shows:
  • Your store’s speed vs. similar stores
  • Top issues to fix
  • Historical performance

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Enable Shopify CDN

Should be enabled by default Verify:
  1. Check if images load from cdn.shopify.com
  2. If not, contact Shopify support
Benefits:
  • Faster global image delivery
  • Reduced server load
  • Better performance worldwide

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Use Shopify’s Image Optimization

Automatic optimization:
  • Shopify resizes images automatically
  • Serves WebP to supported browsers
  • Lazy loads images
Ensure your theme uses: 
{{ product.featured_image | image_url: width: 800 | image_tag }}

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App Compatibility Issues

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Issue: Conflicts with other apps slowing performance

Process:
  1. Note current page speed
  2. Disable apps one by one
  3. Test page speed after each
  4. Identify which app(s) cause slowdowns
Common culprits:
  • Page builders (heavy JavaScript)
  • Review apps (external API calls)
  • Chat widgets (constant polling)
  • Personalization apps (complex logic)
Options:
  1. Find lighter alternatives to heavy apps
  2. Configure apps for lazy loading
  3. Load apps only on specific pages
  4. Contact app developer for optimization
Looksy is optimized: Minimal conflict potential

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Server Response Time

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Issue: Slow Time to First Byte (TTFB)

What it measures: Server response time Target: < 600ms Common causes:
  • Shopify server issues (rare)
  • DNS problems
  • Too many redirects
  • Heavy backend processing
Fix:
  1. Check Shopify status page
  2. Contact Shopify support if consistently slow
  3. Reduce redirects
  4. Optimize Liquid code in theme
Looksy impact: None (runs on separate servers)

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Performance Monitoring

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Set Up Ongoing Monitoring

Free performance monitoringSetup:
  1. Verify site in Google Search Console
  2. Navigate to “Core Web Vitals” report
  3. Monitor ongoing performance
Benefits: See real user metrics, not just lab tests
Built-in monitoringTrack:
  • Online Store Speed report (weekly)
  • Session duration (slower = shorter sessions)
  • Bounce rate (slower = higher bounce rate)
Options:
  • GTmetrix (free, detailed reports)
  • Pingdom (uptime + performance)
  • WebPageTest (advanced analysis)
Use: Monthly check-ins to catch regressions

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Performance Best Practices

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Checklist for Fast Store

  • Product images compressed (< 300KB each)
  • Using WebP format where possible
  • < 15 apps installed
  • Performance-optimized theme
  • Shopify CDN enabled
  • Lazy loading images enabled
  • Minimal third-party scripts
  • Regular performance audits
  • Core Web Vitals in “Good” range
Following these practices ensures your store stays fast with or without Looksy.

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When to Contact Looksy Support

Contact [email protected] if:
  • Page speed decreased immediately after installing Looksy
  • Disabling Looksy significantly improves performance
  • Try-on rendering takes > 10 seconds consistently
  • You see JavaScript errors related to Looksy
Include in your message:
  • Product page URL
  • PageSpeed Insights results (before/after Looksy)
  • Browser console errors (F12)
  • Steps taken to troubleshoot

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Expected Performance Impact

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Normal Looksy Performance

Page Load:
  • Impact: < 0.1 seconds
  • Core Web Vitals: No change
Button Load:
  • Time: < 1 second after page load
  • Async: Doesn’t block rendering
Try-On Rendering:
  • Time: 15-20 seconds (server-side processing)
  • Network-dependent: Slower on poor connections
Mobile:
  • Same as desktop
  • Works well on 4G/5G
  • Graceful degradation on 3G
If you’re seeing worse performance than this, something else is likely the cause. Use the diagnostics above to identify the real bottleneck.

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Common Questions

No. Looksy is optimized for minimal performance impact (< 0.1s). If your store is slow, it’s likely due to large images, too many apps, or theme issues.
Disable Looksy temporarily, run PageSpeed Insights, then re-enable and test again. If scores are the same, Looksy is not the cause.
Unoptimized product images (> 1MB). Compress images to 100-300KB for dramatic speed improvements.
Yes, but fix underlying performance issues first. Looksy won’t make a slow store slower, but customers expect fast experiences overall.

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Next Steps

Will It Slow My Store?

Learn about Looksy’s performance optimization

Common Issues

Fix other common problems

Mobile Optimization

Optimize for mobile performance

Image Quality

Optimize product images for speed and accuracy