Technical SEO basics: redirects, canonicals, status codes and page speed

Content gets a page ranked; technical problems stop it from being seen at all. Most technical SEO work is small and repetitive: one version of each URL, the right status code, pages that load fast on a phone. A screening may show you a few URLs and ask what is wrong.

One URL per page

Search engines treat these as different pages: http:// and https://, www and non-www, trailing slash and none, and ?utm_source=... parameters. If all of them serve the same content, the page competes with itself. Two fixes work together. First, redirect every variant to one chosen form with a 301 (permanent) redirect at the server level. Second, put a canonical tag in the head of every page pointing to its own preferred URL:

<link rel="canonical" href="https://www.example.com/blog/interview-tips/">

Worked example: a product page is reachable at /product/123, /product/123?ref=home and /product/123/. Redirect the slash version to the no-slash version and set the canonical to /product/123. The parameter version now reports the clean URL as canonical, so the tracking link no longer splits ranking signals.

Status codes and redirects

• 200: page is fine. 301: moved for good, passes ranking signals, use for renamed or merged pages. 302: temporary, use only when the old page is coming back.
• 404: page does not exist. Return a real 404 with a helpful page. A "not found" message served with status 200 is a soft 404 and wastes crawl effort.
• 410: gone on purpose. 500 and 503: server errors; if they persist, pages drop out of the index.

Check any URL with curl -I https://www.example.com/old-page and read the first line. Collapse redirect chains to one hop. Never redirect every deleted page to the home page; that is also treated as a soft 404.

Speed and mobile

Search engines index the mobile version of a page first, so the mobile view must have the same content and links as desktop. The Core Web Vitals measure the loading experience: Largest Contentful Paint (how soon the main content appears), Interaction to Next Paint (how fast the page responds to a tap) and Cumulative Layout Shift (how much things jump around). The usual fixes are compressing and sizing images, setting width and height on images and ads so space is reserved, deferring scripts not needed at first paint, and caching. Measure the real article template, not just the home page.

Common mistakes and a practice habit

• Canonical tags pointing to the http version after the site moved to https.
• Using 302 for a permanent move.
• Blocking CSS or JavaScript in robots.txt so the mobile page cannot render.

Practice habit. Pick any site you use. Test the four URL variants with curl, view the source for the canonical tag, and run one page through a speed tool. Write down three findings and the fix for each. One site a week makes the checks automatic.