Technical SEO is the foundation that lets search engines access and understand your site. Without it, even brilliant content sits invisible. The basics break into five areas: crawlability, indexability, site architecture, performance, and security. Start with crawl health. Use Google Search Console to identify 404s, server errors, and redirect chains longer than two hops. Fix broken internal links immediately because they waste crawl budget and fragment PageRank flow. Submit an XML sitemap that lists only canonical, indexable URLs—exclude paginated pages, parameter variations, and anything blocked by noindex. A 500-page site rarely needs more than one sitemap; a 50,000-page portfolio might split them by section. Site structure matters more than most realize. Implement a logical hierarchy where important pages sit within three clicks of the homepage. Use descriptive, keyword-relevant URLs without session IDs or excessive parameters. Canonicalize duplicate content aggressively—specify the preferred version when product pages exist under multiple categories or filter combinations. Mobile-friendliness isn't optional in 2025. Google indexes mobile-first, so test with their Mobile-Friendly Test tool and fix viewport issues, touch-target spacing, and font legibility. Core Web Vitals directly impact rankings: aim for LCP under 2.5 seconds, FID under 100ms, and CLS under 0.1. Real users tolerate slow sites poorly, which kills engagement metrics that indirectly affect rankings. Security basics: run HTTPS sitewide with a valid certificate, set HSTS headers, and redirect HTTP to HTTPS with 301s. Mixed content warnings tank trust and rankings. Structured data amplifies visibility. Add Schema markup for articles, products, local businesses, FAQs, or reviews depending on your content type. Google's Rich Results Test shows what you're eligible for—rich snippets drive measurably higher CTRs in our portfolio. At Ottawa SEO, we audit technical issues before touching content because a technically broken site wastes every other optimization. Fix the plumbing first, then worry about the fixtures. Most sites have 15–40 fixable technical issues; prioritize those blocking indexation or killing user experience, then tackle the refinements.