How do I see the size of a web page?
Why page size matters for SEO and user experience
Page size directly affects how quickly a page loads — every kilobyte of HTML, CSS, JavaScript, image data, and font files must be transferred from the server to the visitor's device before the page can fully render. On a fast broadband connection, a large page may load acceptably. On a mobile connection in a low-signal area, the same page can become frustratingly slow. Since 2021, Google has incorporated Core Web Vitals (which measure actual loading speed and visual stability) as ranking factors, making page size a genuine SEO concern as well as a user experience one.
The biggest contributors to page size
Images are typically the single largest contributor to page size on most websites. An unoptimised photograph can easily be 3-5MB; the same image properly optimised and converted to a modern format like WebP might be 100-200KB — a 90%+ reduction with no visible quality loss for typical web display sizes. JavaScript is often the second-biggest contributor, particularly on sites using large front-end frameworks. Third-party scripts (analytics, advertising, chat widgets, social media embeds) frequently add significant weight that site owners aren't fully aware of because they're loaded from external domains.
How to diagnose which specific assets are slowing your pages
Chrome's developer tools (F12 → Network tab) show every single resource loaded when your page opens, sorted by size or load time. This makes it immediately obvious which specific images, scripts, or stylesheets are the largest. A useful shortcut is to filter by 'Img' to see only images, then sort by size descending — this instantly shows which images should be compressed or resized as a priority. Repeating this for 'JS' and 'CSS' filters reveals whether scripts or stylesheets are contributing disproportionate weight.
Key Takeaways
- Page size directly affects loading speed, which is a Google ranking factor since 2021.
- Images are typically the biggest contributor — unoptimised photos can be 10-30x their optimal size.
- Chrome's F12 Network tab shows every loaded resource sorted by size to pinpoint what to optimise first.