Google rewrites meta descriptions about 60–70% of the time based on multiple industry studies tracking SERP behavior. The rewrite rate varies by query type, niche, and how well your custom description aligns with what the searcher typed. Informational queries see higher rewrite rates than branded searches. Google pulls replacement snippets from visible page content—paragraphs, lists, tables, or structured data—when its algorithm decides those fragments answer the query more directly than your meta tag. A single page can show different descriptions for different keywords, which means your meta description is a suggestion, not a guarantee. Common rewrite triggers include meta descriptions that are too short (under 120 characters), too long (past 155–160 characters on desktop), stuffed with keywords, or generic across multiple pages. Google also rewrites when your description omits the exact phrase someone searched, especially for long-tail queries. If your content covers multiple subtopics, expect Google to cherry-pick relevant sentences for narrower searches. At Ottawa SEO, we still write custom meta descriptions for every important page because the 30–40% of the time Google uses them, they drive measurable CTR lifts in competitive SERPs. We focus on query intent over keyword density, include a clear value hook in the first 120 characters, and avoid duplicate descriptions across the site. We also monitor Search Console's Performance report filtered by page to see which queries trigger our meta versus a rewrite, then adjust content structure when Google consistently ignores our tags. The rewrite rate climbs when you neglect descriptions entirely—Google will always generate something, and auto-generated snippets rarely optimize for click-through. Even if Google rewrites 70% of the time, controlling the other 30% on high-value queries justifies the effort, especially for commercial and transactional pages where CTR directly impacts revenue.