Website Performance and Testing: Questions Answered
How to check whether a website is working, slow or performing well, how to measure page speed and Core Web Vitals, and how to test a site manually before launch.
Each answer below gives the short version first. Open the full article for the steps, the reasons and the official sources.
12 questions on Website Performance and Testing
| Question | Short answer |
|---|---|
| Check Core Web Vitals Once and Fix What Matters | You do not need to check Core Web Vitals daily. Field data updates on a 28-day rolling average, so check LCP, CLS and INP after site changes, after fixing issues, or once a month as part of regular SEO maintenance. |
| Fix Your PageSpeed Score Without an Agency or Subscription | To fix your PageSpeed score, work in order of impact: reduce TTFB first if it is over 600ms using server-side caching, then defer render-blocking scripts, optimise images to WebP, enable GZIP or Brotli compression and remove unused JavaScript. Most fixes need no agency. |
| How can I test if a website is working? | Open the website in a browser for a quick check, then use an online uptime checker that tests it from several locations. A good checker reports whether the domain resolves, how fast the server responds and which HTTP status code comes back. A code in the 5xx range means the server itself is failing. |
| How to check if a website is experiencing issues? | Check the site with an independent status checker that tests it from external servers. If the checker says the site is down, the problem is on the site's side. If it says the site is up but it will not load for you, the problem is local, so clear your cache, try another browser or switch to mobile data. |
| How to QA test a website? | Agree what working correctly means for each feature, decide which browsers and devices to cover, and prepare realistic test data. Then run manual and automated checks, log each defect with steps to reproduce it, retest every fix, and finish with a full regression test before launch. |
| How to test a website manually? | Write test cases for the key user journeys, such as sign-up, checkout and forms, each with a clear expected result. Run them in Chrome, Firefox, Safari and Edge on different screen sizes, try unusual inputs as well as normal ones, and record every problem with exact steps to reproduce it. |
| How do I see the size of a web page? | Open your browser's developer tools (press F12), go to the Network tab and reload the page. It lists every file the page loads, including images, scripts, stylesheets and fonts, with their sizes and the page total. Images are usually the largest part. |
| How do I check how my website is performing? | Check speed and Core Web Vitals with Google's PageSpeed Insights, which is free. Check search performance (indexing, rankings, clicks and search terms) in Google Search Console, and check visitors and conversions in your analytics. Speed tells you how the site feels to use, while Search Console tells you how it is doing in search. |
| What is the best tool for page speed testing? | Google's PageSpeed Insights is the best starting point. It is free, measures Core Web Vitals, and shows both a simulated test and real-world data from Chrome users. Other tools add detailed loading charts and tests from different locations. Scores differ between tools because they measure differently, so use more than one. |
| How do I check if a website is slow? | Run the page through a speed tool such as Google's PageSpeed Insights and look at Largest Contentful Paint. Google rates under 2.5 seconds as good. In the browser, press F12 and use the Network tab to see which files take longest to load. Test on a simulated slow mobile connection and at different times of day. |
| How do I know if my website is performing well? | Check four things: Core Web Vitals in the good range (in PageSpeed Insights or Search Console), no crawling or indexing problems in Google Search Console, organic traffic that is steady or growing, and conversions moving the right way in your analytics. Compare with the same period last year, because traffic changes with the seasons. |
| Browser Caching Without ?v= Tags: Revalidation Explained | Revalidation is a browser caching approach where the browser keeps a file but checks with the server before using it. With Cache-Control: no-cache and ETags, the server replies 304 Not Modified if nothing changed or 200 with the new file, so JavaScript and CSS updates reach visitors on their next page view without ?v= tags. |