SEO Glossary
10 essential SEO terms defined with implementation tips and links to in-depth guides. We add new terms weekly.
What Is Domain Rating (DR)? Definition & How to Improve It
Domain Rating (DR) is Ahrefs' proprietary score (0–100) measuring a website's backlink profile strength. Learn how DR is calculated and proven tactics to raise your score.
What Are Backlinks? SEO Definition, Types & How to Earn Them
Backlinks are inbound links from other websites to yours — a top Google ranking factor. Learn the difference between dofollow and nofollow links and how to earn high-quality backlinks.
What Is Crawl Budget? SEO Definition & Optimization Guide
Crawl budget is the number of pages Googlebot crawls on your site per day. Learn what controls it, why it matters for large sites, and how to optimize it so your most important pages get indexed first.
What Is Schema Markup? SEO Definition, Types & Implementation
Schema markup is JSON-LD structured data that helps Google understand your content and display rich results (stars, FAQs, how-tos) in SERPs. Learn the most valuable schema types for SEO.
What Is Alt Text? SEO & Accessibility Definition with Examples
Alt text is an HTML image attribute that describes visuals for search engines and screen readers. Learn how to write descriptive, keyword-rich alt text that improves image SEO and accessibility.
What Is a Canonical Tag? Definition, When to Use It & Common Mistakes
A canonical tag (rel="canonical") tells Google which URL is the authoritative version of a page when duplicate content exists. Learn when to use it, how to implement it correctly, and the mistakes that silently hurt rankings.
What Is a Title Tag? SEO Definition, Best Length & Writing Tips
A title tag is the HTML element that sets a page's clickable headline in Google search results. Learn the optimal length (50–60 characters), how to front-load keywords, and why Google rewrites 60% of title tags.
What Is a Meta Description? Definition, Length & CTR Best Practices
A meta description is the short summary shown under your page title in Google SERPs. It doesn't directly affect rankings, but a well-written one significantly improves click-through rate. Learn the ideal length (140–160 characters) and how to write them.
What Is Noindex? How the Meta Robots Tag Controls Indexing
Noindex is a robots meta tag directive that prevents a page from appearing in Google search results. Learn when to use noindex vs. nofollow vs. robots.txt disallow, and the common mistake that makes noindex invisible to crawlers.
What Are Open Graph Tags? Definition & Guide to Social Previews
Open Graph tags are HTML meta tags that control how your pages look when shared on Facebook, LinkedIn, X, and Slack. Learn the four essential OG tags, ideal image dimensions (1200×630px), and how they interact with Twitter Cards.