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How Much a Slow Website Costs You, and How to Make It Fast from Day One

Speed affects both your Google ranking and how many visitors buy. How to measure it, which numbers matter, and how we build sites to be fast from the start.

5 min read

SEOความเร็วเว็บWeb Development

Short answer: most visitors arrive on a phone, and if the first screen takes several seconds, many leave before they see anything. Google also uses speed (Core Web Vitals) as a ranking factor. A fast site gets more visitors and keeps them longer.

How to measure speed

Open Google PageSpeed Insights, enter your URL and look at the mobile results. Three numbers matter:

LCP
What it measures: How fast the main content appears
Good value: 2.5 s or less
INP
What it measures: How fast the page responds to a tap
Good value: 200 ms or less
CLS
What it measures: Whether the page jumps around while loading
Good value: 0.1 or less

Common reasons sites are slow

  • Oversized images that were never resized or converted to WebP/AVIF.
  • Lots of plug-ins and third-party scripts: chat widgets, pop-ups, multiple trackers.
  • Pages built entirely by JavaScript in the browser, which is slow on older phones.
  • A distant or undersized server with no caching.
  • Many fonts and weights loading at once.

How we build for speed from the start

We use Next.js, which renders pages on the server, so Google reads the content immediately and visitors see the page without waiting for JavaScript. Images are resized and converted automatically, only the fonts in use are loaded, and third-party scripts are kept to what is needed.

During development we run Lighthouse every time we deploy to staging, so you see the scores before launch instead of fixing them afterwards.

My current site is slow. Do I need a rebuild?

Not always. If the problem is images, plug-ins or the server, it can usually be fixed in place. If the site is old and every fix breaks something else, rebuilding on the right foundation is often cheaper in the long run.

See our web development service

FAQ

Does speed really affect SEO?

Yes. Core Web Vitals are a ranking factor, and slow pages make people leave, which hits sales directly.

Do I need a PageSpeed score of 100?

No. Focus on keeping mobile LCP, INP and CLS in the good range.

Why Next.js?

It renders on the server so Google reads content immediately, and it handles images, fonts and SEO metadata out of the box.

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