A meta description is HTML code in your page's <head> that tells search engines what summary to display under your title in the SERPs. You write it in your CMS's SEO section or directly in HTML using <meta name="description" content="Your text here">. Google uses it roughly 40% of the time—they rewrite it when they think their auto-generated snippet better matches the query. Start with the primary keyword in the first 120 characters because mobile cuts off around there. Answer the search intent immediately. If someone searched "how to fix a leaky faucet," your description should say "Learn how to fix a leaky faucet in 5 steps using basic tools" not "Welcome to our plumbing blog where we discuss various topics." You're writing ad copy, not a summary. Stay between 150–160 characters. Longer descriptions get truncated with an ellipsis, shorter ones waste real estate. Include a call like "See how" or "Get the checklist" when it fits naturally. Avoid duplicate descriptions across pages—every page needs its own because they target different queries. Common mistakes: stuffing keywords (looks spammy, users won't click), writing for bots instead of humans (CTR tanks), or leaving it blank (Google pulls random sentences, often terrible ones). We see roughly 1–3 percentage point CTR differences between a generic description and one tailored to user intent, which compounds over thousands of impressions. At Ottawa SEO we write descriptions after the page content is final, not before, because you need to know what you're actually promising. For portfolio sites with 500+ domains, we use templates with dynamic fields for product names or locations, then manually review high-traffic pages. The description won't make you rank, but it's often the tiebreaker when you're in position 3–5 against similar competitors. If your CTR is 2% and theirs is 5%, they win even if you technically rank higher.