What an on-page audit covers
On-page SEO is everything on the page itself that helps search engines understand it and helps people click it: the title and description, one clear H1, a sensible heading outline, enough useful text, descriptive image alt text, internal links, a canonical URL, structured data, and a page that loads quickly on a phone.
This checker reads the page the way a crawler does, from the HTML the server returns, and scores each of those areas. It does not replace a full crawl of your site, but it finds most problems on a single page in seconds.
How the score works
Each check passes, warns or fails, and each has a weight: a missing title costs more than a long one. The score is the share of points earned. Aim to clear every failed check first; warnings are improvements, not emergencies.
Questions
Is a high score a guarantee of ranking?
No. On-page work makes a page eligible to rank; links, competition and how well the page answers the search decide the rest.
Does it check JavaScript-rendered content?
No. It reads the server HTML, as many crawlers do on the first pass. If your content only appears after JavaScript runs, consider server rendering.
How many words should a page have?
Enough to answer the search completely. Pages under about 300 words are flagged because they are often too thin to rank, not because of a magic number.
Can I audit my competitors?
Yes, any public page. The SEO compare tool puts two pages side by side.