Published 17 Jun 2026
Website Speed Optimization Checklist: 15 Things to Fix in 2026
Use this website speed optimization checklist to improve load time, Core Web Vitals, mobile performance, user experience, and technical SEO before hiring an expert.
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Website Speed Optimization Checklist: Quick Summary
A website speed optimization checklist helps you find and fix the issues that slow down your website. The most important areas to check are Core Web Vitals, image size, caching, mobile performance, JavaScript, CSS, hosting, fonts, third-party scripts, and post-optimization testing.
Website speed does not guarantee rankings, but it can support SEO by improving page experience, reducing user frustration, and making your site easier to use across devices. If you need help applying these fixes, you can hire a website speed optimization expert on Osdire.
Website Speed Optimization Checklist for 2026
Use this checklist to review the most common website performance issues before making changes or hiring a specialist.
| # | What to Check | How to Measure It |
| 1 | Test current website speed | Use PageSpeed Insights, Lighthouse, GTmetrix, or WebPageTest |
| 2 | Check Core Web Vitals | Review LCP, INP, and CLS in PageSpeed Insights or Search Console |
| 3 | Improve LCP | Aim for Largest Contentful Paint under 2.5 seconds |
| 4 | Improve INP | Aim for Interaction to Next Paint under 200 ms |
| 5 | Improve CLS | Aim for Cumulative Layout Shift under 0.1 |
| 6 | Compress large images | Check image size and PageSpeed image warnings |
| 7 | Use next-gen image formats | Use WebP or AVIF where possible |
| 8 | Enable lazy loading | Check whether below-the-fold images load only when needed |
| 9 | Reduce render-blocking resources | Review PageSpeed warnings for blocking CSS or JavaScript |
| 10 | Minify CSS and JavaScript | Check Lighthouse warnings for unused or unminified code |
| 11 | Remove unused plugins, apps, or scripts | Review plugin/app lists and third-party script load |
| 12 | Improve server response time | Check TTFB in PageSpeed, GTmetrix, or WebPageTest |
| 13 | Use caching and a CDN | Check cache headers, CDN setup, and repeat-visit load time |
| 14 | Optimize font loading | Review font file size, loading behavior, and layout shift |
| 15 | Retest after changes | Compare before-and-after scores and Core Web Vitals |
1. Test Your Current Website Speed First
Before fixing anything, test your current website speed. This gives you a baseline so you can compare results later.
Useful tools include:
- Google PageSpeed Insights
- Lighthouse
- GTmetrix
- WebPageTest
- Google Search Console
Check both mobile and desktop results. Mobile performance is especially important because many users browse, shop, and submit forms from mobile devices.
2. Check Core Web Vitals
Core Web Vitals are performance signals that help measure page experience. The three key metrics are:
- LCP: how quickly the main content loads
- INP: how quickly the page responds to user interaction
- CLS: how stable the page layout is while loading
Use PageSpeed Insights or Google Search Console to check whether your pages pass or fail Core Web Vitals.
3. Improve Largest Contentful Paint
Largest Contentful Paint, or LCP, measures how long it takes for the main visible content to load. A slow LCP can make the page feel delayed even if other elements load quickly.
Common LCP fixes include:
- Compressing hero images
- Reducing server response time
- Removing render-blocking resources
- Using a CDN
- Preloading important assets
- Improving hosting performance
A good LCP target is under 2.5 seconds.
4. Improve Interaction to Next Paint
Interaction to Next Paint, or INP, measures how quickly a page responds after a user interacts with it. Poor INP can make buttons, menus, filters, or forms feel slow.
Common INP fixes include:
- Reducing heavy JavaScript
- Removing unnecessary scripts
- Optimizing third-party tools
- Splitting long tasks
- Improving frontend code
A good INP target is under 200 milliseconds.
5. Improve Cumulative Layout Shift
Cumulative Layout Shift, or CLS, measures how much the page layout moves while loading. High CLS can cause users to click the wrong button or lose their place on the page.
Common CLS fixes include:
- Setting image width and height
- Reserving space for ads or embeds
- Optimizing font loading
- Avoiding late-loading banners
- Reducing layout shifts from dynamic content
A good CLS target is under 0.1.
6. Compress Large Images
Large images are one of the most common causes of slow websites. Compress images before uploading them and avoid using oversized files.
Check:
- Hero images
- Product images
- Blog images
- Background images
- Gallery images
Use the right dimensions for each placement instead of uploading large files everywhere.
7. Use WebP or AVIF Images
Next-generation image formats such as WebP and AVIF can reduce file size while keeping good visual quality. Use these formats where your website platform supports them. This is especially useful for ecommerce stores, image-heavy blogs, portfolio sites, and landing pages.
8. Enable Lazy Loading
Lazy loading delays below-the-fold images until the user scrolls near them. This can improve initial page load time because the browser does not need to load every image at once.
Use lazy loading for:
- Blog images
- Product grids
- Galleries
- Related posts
- Below-the-fold media
Avoid lazy loading the main hero image if it is important for LCP.
9. Reduce Render-Blocking Resources
Render-blocking resources can delay the page from appearing quickly. These are usually CSS or JavaScript files that the browser must load before showing content.
Common fixes include:
- Deferring non-critical JavaScript
- Inlining critical CSS
- Removing unused code
- Loading scripts only where needed
- Reducing heavy theme files
This often requires developer-level support.
10. Minify CSS and JavaScript
Minification removes unnecessary spaces, comments, and characters from code files. Smaller files can load faster.
You should also check for unused CSS and JavaScript. Many websites load code from themes, plugins, apps, and tracking tools that are no longer needed.
11. Remove Unused Plugins, Apps, and Scripts
Plugins, apps, tracking tags, chat widgets, popups, and marketing scripts can slow down a website.
Review:
- WordPress plugins
- Shopify apps
- Tracking pixels
- Chat widgets
- Popup tools
- Social embeds
- Old analytics scripts
Keep only what is useful and remove tools that no longer support the business.
12. Improve Server Response Time
Server response time affects how quickly the browser receives the first response from your website. Slow hosting, overloaded servers, poor caching, or heavy backend processes can increase response time.
Check TTFB, or Time to First Byte, using PageSpeed Insights, GTmetrix, or WebPageTest.
If server response time is slow, you may need better hosting, caching, database cleanup, or backend optimization.
13. Use Caching and a CDN
Caching stores parts of your website so pages can load faster on repeat visits. A CDN, or content delivery network, helps serve files from locations closer to the visitor.
Caching and CDN setup can help with:
- Static assets
- Images
- CSS files
- JavaScript files
- Repeat visits
- Global traffic
This is useful for ecommerce stores, blogs, SaaS sites, and international websites.
14. Optimize Font Loading
Fonts can slow down pages or cause layout shifts if they are not loaded properly.
Check:
- Number of font families
- Number of font weights
- Font file size
- Display behavior
- Layout shift caused by font swapping
Use fewer font weights and load only the fonts your website actually needs.
15. Retest After Every Major Change
After making speed improvements, test the website again. Compare the new results with your baseline.
Track:
- PageSpeed Insights score
- LCP
- INP
- CLS
- TTFB
- Mobile performance
- Desktop performance
- Real user data if available
Do not rely only on one score. Look at the full picture, including user experience and Core Web Vitals.
Website Speed Optimization by Platform
Different platforms need different speed fixes.
- WordPress: Focus on plugins, themes, caching, image optimization, database cleanup, hosting, and Core Web Vitals.
- Shopify: Focus on apps, theme code, images, scripts, Liquid files, product pages, and checkout-related performance where possible.
- WooCommerce: Focus on hosting, database performance, plugins, product images, cart pages, checkout speed, and caching.
- Wix: Focus on image size, page structure, mobile performance, embeds, and built-in platform limitations.
- Magento: Focus on caching, hosting, extensions, database load, product pages, and server-side performance.
- Custom websites: Focus on code quality, hosting, frontend assets, APIs, scripts, caching, and deployment setup.
When Should You Hire a Website Speed Optimization Expert?
You should hire a website speed optimization expert if your site is slow, mobile performance is poor, Core Web Vitals are failing, or simple fixes are not enough.
A freelancer can help with:
- Speed audits
- Core Web Vitals fixes
- Image optimization
- Caching setup
- JavaScript and CSS cleanup
- Shopify or WordPress speed issues
- Ecommerce performance
- Developer-level technical fixes
If you want expert help, you can compare website speed optimization services on Osdire and choose a freelancer based on scope, pricing, platform experience, and delivery time.
FAQs
What is a website speed optimization checklist?
A website speed optimization checklist is a list of technical and content-related checks used to improve load time, mobile performance, Core Web Vitals, and user experience.
What is the most important website speed metric?
Core Web Vitals are important because they measure real page experience. The key metrics are LCP, INP, and CLS.
How do I check what is slowing down my website?
Use PageSpeed Insights, Lighthouse, GTmetrix, WebPageTest, and Google Search Console. These tools can show issues with images, scripts, server response time, Core Web Vitals, and mobile performance.
Does website speed optimization help SEO?
Website speed optimization can support SEO by improving page experience, technical performance, and user engagement. It does not guarantee rankings, but it can make pages easier for users and search engines to access.
When should I hire a website speed optimization expert?
Hire an expert when your website has poor Core Web Vitals, slow mobile performance, heavy scripts, technical issues, ecommerce speed problems, or performance issues that need developer-level fixes.
