I spent 3 hours debugging why Google couldn't crawl my React app. No 404s, no console errors, nothing obviously broken. The culprit? A missing <title> tag, a robots meta set to noindex from a staging environment I'd forgotten to revert, and a canonical URL pointing to http:// instead of https:// . Three separate mistakes. Four lines of code to fix them. Zero obvious symptoms while I was building. If you've ever shipped a site and wondered why it isn't ranking — even when the content is solid — there's a good chance you're living with quiet SEO mistakes right now. This guide walks through the most common ones, how to detect them programmatically, and how to fix them before they cost you traffic. Mistake #1: Your <head> Is a Disaster and You Don't Know It The most common SEO mistake in SPAs (React, Next.js, Remix) is inconsistent or missing meta tags across dynamic routes. The homepage looks fine. The blog post at /blog/some-slug ? No description, wrong canonical, og:title still says your app name.…
