An on-page SEO checker reads the HTML of a page and tests it against known good practice. It cannot judge whether your content is the best answer on the web, but it reliably finds the technical and structural problems that stop a good page from performing. Here is what these checks cover and what to do with the results.
Title tag and meta description
The checker looks for a title on every page, flags missing, empty or duplicate titles and warns when a title is likely to be truncated in results (roughly beyond 60 characters). For the meta description it checks presence, uniqueness and length. A common finding is the same title and description on many pages because they come from one template. The fix is to generate them from page-specific data such as the product, service or article name.
Headings
A page should have one H1 that states its topic, followed by H2 and H3 headings that organize the content. Typical findings are no H1, several H1 elements, headings used only for styling and skipped levels. Headings help readers scan and help search engines understand the structure, so write them as short descriptions of the section.
Content signals
Checkers measure the amount of real text on the page, the ratio of text to code and signs of keyword stuffing. A page with very little text rarely satisfies a search query. The fix is not to add words for their own sake: add the information a visitor expected to find, such as details, examples and answers to follow-up questions.
Images
The usual checks are missing alt text, oversized files and missing dimensions that cause layout shift. Write alt text that describes the image for someone who cannot see it. Compress images and serve them at the size they are displayed.
Links
Internal links show crawlers which pages matter and let visitors move around. The checker finds broken internal links, links that go through redirects and important pages that few other pages link to. Use descriptive anchor text, not "click here". For external links, check that they are not broken.
Canonical, robots and indexing directives
On each page the checker reads the canonical tag and robots directives. It flags a canonical pointing to a different or broken URL, a noindex on a page you want in search and conflicting signals between the tag and HTTP headers. These findings are high priority because they can remove a page from search results.
Structured data and social tags
Structured data in JSON-LD, such as Article, Product, FAQPage or Organization, helps search engines understand the page and can make it eligible for rich results. The checker validates that the markup is present and well formed. Open Graph tags control how the page looks when shared, and are checked at the same time.
Language and international signals
If a site has several language versions, the checker validates hreflang codes and the return links between versions. A language version that does not link back is ignored by search engines, so these errors are easy to miss and worth fixing.
How to read the results
- Errors first. Anything that blocks indexing or breaks the page, such as noindex or a wrong canonical.
- Repeated warnings next. A problem that appears on every page, like a duplicate title, is usually a single template fix.
- Single-page warnings last. Alt text and heading polish matter, but have the smallest effect.
Treat the score as a guide, not a goal. A page can score well and still not rank because the content does not match what people are searching for.
A quick example of reading one finding
Say the report shows "title too long" on forty pages. Open two of them and look at the title. If every title ends with the same long site name, the cause is the template that appends it. Shorten the suffix once, and forty warnings disappear. If instead the titles are long because each describes the page in great detail, you have a content decision: keep the most important words at the start, since the end may be cut off in results.
The same approach works for other findings. Ask where the problem comes from, whether it is one template or many editors, and fix it at that level. A checker tells you what is wrong. Finding the cause is your job.
What an on-page checker does not do
It does not measure rankings, traffic or backlinks, and it does not decide whether your content is better than a competitor's. Pair it with Search Console for real query data. For the wider technical picture, use the technical SEO audit checklist.
FAQ
How is on-page SEO different from technical SEO?
On-page SEO covers what is on a single page: titles, headings, content, images and links. Technical SEO covers how the whole site is crawled, rendered and served. The two overlap and are usually checked together.
Can an on-page checker check competitors?
Yes. Any public page can be scanned, which helps you see how competing pages structure their titles, headings and markup.
How many warnings are normal?
Most real sites have some. Focus on errors and repeated issues rather than trying to reach zero warnings.
Check your own website
Reading a checklist is useful, but a scan shows what is actually wrong on your site. Run a free SEO check, enter your domain and get a score for each area with a ranked list of fixes. The baseline report needs no account. You can also read what the SEO checker analyzes or open the free SEO check page for an example report.