A webpage size checker measures how heavy a page is. This tool measures the HTML document of any public URL: it fetches the page and reports the raw HTML size in kilobytes and an estimated compressed (gzip) size. HTML is the first file a browser downloads, so a bloated document delays everything after it.
Reading the result: up to 100 KB of raw HTML is within the recommended range, 100–200 KB gets a warning, and more than 200 KB is flagged as very large. The gzip figure is an estimate (30% of the raw size); real compression depends on the content and the server. Large HTML usually comes from inline scripts and styles, embedded data such as big JSON objects from JavaScript frameworks, inline SVGs, or very long pages.
Limits: this measures the HTML only. It does not add up images, CSS, JavaScript or fonts, so it is not the total page weight. For the total, open the Network tab in your browser's developer tools or run PageSpeed Insights, which list every resource and its size. The page must respond within 15 seconds and be under 5 MB.