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What is On-Page SEO score and how is it calculated?

onpage_score is an OnPage API proprietary metric that estimates the quality of technical page optimization. It considers critical on-page errors and warnings detected on the page.

The score is provided on a 100-point scale. 100 is the highest possible score indicating that the page doesn’t have any critical errors and warnings and thus is well optimized. 0 is the poorest score, meaning that the page accumulates all the possible errors and warnings and thus is not optimized at all.

The metric can be found in the following endpoints:


In the majority of endpoints, onpage_score provides the score for a single page. However, in the Summary endpoint, the score is related to all pages of a domain. To learn how the onpage_score of a domain is calculated, refer to this article.

How is On-Page Score calculated?

OnPage API divides on-page issues into two categories: critical errors and warnings. Each issue has its own value that is used as a variable in the calculation.

The score is calculated by the following formula:

Sc = 100 – ∑(En/78) x 55 – ∑(Wn/123) x 45

Assume that the page failed two checks from the Errors category (let it be high_loading_time and is_http) and two checks from the Warnings category (duplicate_title, no_image_alt). In this case, the calculation will be performed as in the following example:

1 First, we calculate the score of each check.



10 / 78 * 55 = 7.05.


8 / 78 * 55 = 5.64



10 / 123 * 4 = 3.65


8 / 123 * 45 = 2.92

2 Then, we sum up the check scores.


7.05 + 5.64 = 12.69


3.65 + 2.92 = 6.57

3 Finally, we subtract the resulting values from the maximum possible OnPage score:

100 – 12.69 – 6.57 = 80.74

4 The onpage_score in this case is 80.74

Critical errors:

Error name Error description Value if true Value if false
high_loading_time page loads longer than 3 seconds 10 0
redirect_loop page has a redirect chain that starts and ends at the same URL (e.g., Page A redirects to Page B, Page B redirects to Page C, and Page C redirects back to Page A) 10 0
canonical_to_broken page with the canonical link element points to a 404 page 9 0 recursive_canonical page contains rel=”canonical” tag to another page, which in turn, refers back to the initial page 9 0 is_http page has an insecure HTTP protocol 8 0 no_title page has no title tag 7 0 duplicate_title_tag page has more than one title tag 5 0 broken_links page has links to broken pages 5 0 links_relation_conflict page has a mix of both follow and nofollow incoming internal links 5 0 canonical_to_redirect canonical page points to a page that redirects elsewhere 3 0 canonical_chain canonical page points to a page that has a canonical pointing elsewhere 3 0 duplicate_content page has duplicate content 4 0 Total value of all errors = 78 Maximum OnPage score = 55


Warning name Warning description Value if true Value if false
duplicate_title page has duplicate title tags 10 0
broken_resources page contains broken resources 10 0
large_page_size the size of a page exceeds 256 kbytes 10 0 duplicate_description page has duplicate description tags 9 0 no_image_alt page has images without alt tags 8 0 seo_friendly_url page with SEO-friendly URL 0 7 flash page has flash elements 5 0 no_description page has an empty description tag 5 0 duplicate_meta_tags page has more than one meta tag of the same type 5 0 no_h1_tag page has an empty h1 tag 5 0 irrelevant_description description tag of a page is irrelevant to its content 5 0 title_too_long title tag of a page exceeds 65 characters 5 0 is_orphan_page page has no internal links pointing to it 5 0 irrelevant_title title tag of a page is irrelevant to its content 5 0 title_too_short title tag of a page is shorter than 30 characters 5 0 no_doctype page has no doctype 4 0 high_content_rate page has the plaintext size to page size ratio of more than 0.9 3 0 low_character_count page has less than 1024 characters 3 0 high_character_count page has more than 256,000 characters 3 0 low_readibility_rate page scored less than 15 points on the Flesch–Kincaid readability test 3 0 deprecated_html_tags page has deprecated HTML tags 3 0 lorem_ipsum page has lorem ipsum content 3 0 Total value of all warnings = 123 Maximum OnPage score = 45
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