On-page SEO checker for Chrome

Q: Does an empty alt attribute count as missing?

No. Only images with no alt attribute at all are flagged. alt="" is the correct way to mark a purely decorative image, so it passes.

Screen Ruler checks the page you are looking at for common on-page SEO problems, from title length to missing alt text, and lists each one with a fix.

What it checks

The SEO Issues section in the side panel's Page tab runs these checks on the page and lists every problem it finds, with a short explanation and a recommendation:

Title: missing <title>, shorter than 30 characters, or longer than 60.
Meta description: missing, shorter than 70 characters, or longer than 160.
H1 heading: no <h1> at all, or more than one.
Canonical link: no <link rel="canonical">.
Viewport: no viewport meta tag for mobile rendering.
Language: no lang attribute on <html>.
Robots: the page is set to noindex.
Images: <img> elements with no alt attribute.
Open Graph: missing og:title, og:description or og:image.

Issues are sorted by severity. Errors come first (a missing title, H1 or viewport tag), then warnings, then informational notes such as a missing canonical link or a page set to noindex, which may be intentional.

How to check a page's SEO

Open the page you want to check.
Start Screen Ruler by clicking its toolbar icon or pressing Alt + Shift + S (Option on a Mac).
In the side panel, switch to the Page tab and find SEO Issues. The heading shows how many issues were found.

If the section is not there, the page passed every check. After you fix something, reload the page or click the refresh button next to the page title to run the checks again.

Finding the problem on the page

Two checks point at specific elements. When a page has several <h1> tags, or several images without alt text, they are grouped into one card with a count. Click the card, or use its arrows, to step through each one: the page scrolls to the element and highlights it, and the card shows its selector. That makes it quick to find the stray heading in a footer or the decorative image that needs alt="".

What makes it different from a crawler

Screen Ruler checks the page as your browser rendered it, after JavaScript has run. That has some practical advantages:

It sees what scripts add. Titles, meta tags and headings set by a single page app are checked as they end up, not as they appear in the raw HTML.
It works anywhere you can open a page. Local development servers, staging sites and logged-in areas can be checked without exposing them to an online tool.
Components are included. Headings and images inside open shadow roots are counted.

What it does not check

This is an on-page check of one page at a time. It does not crawl your site, find broken links or duplicate content across pages, read robots.txt or sitemaps, check HTTP status codes or redirects, validate structured data, or tell you anything about rankings, keywords or backlinks. Use it for fast checks while you build and review, and a dedicated SEO crawler for site-wide audits.

When it is useful

Before you publish. Check a new landing page or blog post for a missing description or an overlong title.
Reviewing a client site. Spot the basics that are missing in a few seconds.
Auditing a template. Open a few pages built from the same template to see whether a problem is a one-off or repeated across the site.
Developing locally. Catch a missing lang attribute or viewport tag while the page is still on your machine.

See the full tag values in the meta tag inspector, check how a link will look when shared with social preview, and check image and script sizes with page weight.

SEO issue detection is free in Screen Ruler, with no time limit.

Common questions

Is this SEO checker free?

Yes. SEO issue detection is one of Screen Ruler's free features, along with the meta tag inspector and social preview, and has no time limit.

What title and description length does it recommend?

Screen Ruler flags titles under 30 or over 60 characters and recommends 50 to 60. It flags descriptions under 70 or over 160 characters and recommends 120 to 160, since longer text may be truncated in search results.

Does an empty alt attribute count as missing?

No. Only images with no alt attribute at all are flagged. alt="" is the correct way to mark a purely decorative image, so it passes.

Can it check pages that render with JavaScript?

Yes. It reads the page as your browser rendered it, so titles, meta tags and headings that a framework sets after load are checked in their final state.