SEO Checkup — On-Page SEO Inspector

About

SEO Checkup is a lightweight, privacy-first on-page SEO inspector. Click the icon on any webpage to instantly see a full SEO health report — right on the page, not hidden in a tiny popup.
 
WHAT IT DOES
 
When you click the extension icon (or press Alt+S), a side panel slides in from the right edge of the page. It scans the current page's DOM and displays a comprehensive SEO audit organized into six categories:
 
▸ Title & Meta
Shows your page title with character count and whether it fits within Google's ~580px SERP display width. Checks the meta description length (optimal range: 120–160 characters). Verifies the canonical tag exists and is self-referencing. Displays the robots meta directive if present.
 
▸ Heading Hierarchy
Renders a visual tree of all H1 through H6 tags in document order, indented by level. Flags common issues: missing H1, multiple H1 tags on the same page, and skipped heading levels (e.g. jumping from H1 directly to H3).
 
▸ Images
Counts all images on the page and breaks them into three groups: images with proper alt text, images with empty alt attributes, and images completely missing the alt attribute. Each image missing alt text is also highlighted directly on the page with a red badge.
 
▸ Links
Categorizes every link on the page into internal vs. external. Separately counts links marked with rel="nofollow", rel="ugc", or rel="sponsored" so you can quickly audit your link equity distribution.
 
▸ Hreflang
Lists all hreflang alternate tags found in the page head. If no hreflang tags are present, the panel notes this with guidance on when they are needed (multilingual or multi-regional sites).
 
▸ Schema & Open Graph
Detects JSON-LD structured data and lists the @type values found (e.g. Product, Article, FAQ). Checks whether Open Graph tags (og:title, og:description, og:image) and Twitter Card meta tags are set.
 
HEALTH SCORE
 
Every page gets a weighted score from 0 to 100 and a letter grade (A+ through F). The score is broken down by category with color-coded dots (green/yellow/red) so you can see at a glance which areas need attention. This is not an arbitrary number — each category has defined scoring rules based on widely accepted SEO best practices.