See what blocks the first paint
Most slow first paints come down to the same few files. Toggle the fixes and watch First Contentful Paint move on a simulated slow phone.
Website speed optimization checklist
Twelve fixes, ordered by how often they make the biggest difference. Tick them off as you go; your progress stays in this browser.
0 of 12 done
HTML document
styles.css (render-blocking)
app.js in <head> (render-blocking)
font.woff2 (new origin: DNS + TLS first)
First paintFCP 1.9 s
First Contentful Paint ≈ 1.9 s → Needs improvement
Magenta bars block rendering: the browser won't paint until they finish. Simplified model of a mobile load with 600 ms server response; real pages have more files, but the rule is the same.
Where to start
Run the speed test first (or the page size checker for a quick weight check) and look at “What to fix first”: Lighthouse ranks opportunities by estimated time saved on your actual page. Fix the failing Core Web Vital before chasing the score, and fix mobile before desktop. For a step-by-step plan for your platform, use the fix-plan button on the results.
Questions people ask
How do I make my website run faster?
Test it first so you fix the right thing. Then, in order: cache your HTML at a CDN, resize and convert images, defer non-essential JavaScript and third-party tags, reserve space for late content, and set long cache lifetimes on static files. The platform guides cover WordPress, Shopify, Wix and Squarespace specifics.
Why are websites so laggy?
Mostly JavaScript. Large frameworks, ad and tracking tags, chat widgets and A/B testing tools keep the main thread busy, so taps and scrolls wait. Heavy images and slow servers make the first load slow on top of that.
What is the fastest way to improve page speed?
On most sites: compress and properly size images (especially the hero image), defer non-essential JavaScript and third-party tags, and cache HTML at a CDN. Those three usually fix LCP and TBT together.
Do I need a developer to speed up my website?
Not always. On WordPress, a caching plugin, an image optimisation plugin and removing unused plugins cover a lot. On Shopify, removing unused apps and oversized theme images helps most. Structural fixes, such as JavaScript bundle size, need a developer.
How much does site speed affect conversions?
Studies published on web.dev by companies including Vodafone and Rakuten 24 linked Core Web Vitals improvements to higher sales and conversion rates. The effect varies by site, so measure your own before and after.