Technical SEO

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Technical SEO is the ground floor that everything else is built on. If the ground floor is cracked, good writing and great titles sitting on top of it will not help much.

Technical SEO is the foundation layer Three stacked layers: technical SEO at the bottom, on-page SEO in the middle, content and off-page SEO on top. A crack in the bottom layer means the layers above cannot stand. Content & Off-page SEO On-page SEO Technical SEO (the foundation) crack here = nothing above can stand
Technical SEO holds up on-page SEO and content SEO. If the foundation breaks, the layers above it cannot stand on their own.

Two of the tools below work very differently, even though both keep a page out of search results. One is a locked gate. The other is only a posted sign.

robots.txt is a gate before crawling; noindex is a sign before indexing Your page, then crawl, then index. robots.txt sits on the path into crawl, like a gate. noindex sits on the path into the index, like a posted sign. Your page robots.txt a request to stay out Crawl noindex a posted request Index
robots.txt stands like a gate on the way to being crawled. noindex is a sign asking to be left off the index, written as a tag or a header, not a locked door.

robots.txt

This file works like a small sign at the door of certain parts of your site: "please don't come in here." A crawler that follows the sign will not walk in. But the sign by itself does not remove a page from search results — it only asks the crawler to stay away. See this site's own robots.txt.

sitemap.xml

This file is the opposite of a "stay out" sign: it is a list you hand to the crawler that says "please visit these pages." See this site's own sitemap.xml. You can also hand this same list to Google Search Console.

canonical

Sometimes two pages on a site say almost the same thing. A canonical tag works like a sticky note on the copy that says "the real one is over here" — it tells search engines which page to show in results.

noindex

Unlike a locked gate, noindex is a posted request: it tells a search engine "please don't put this page on your list." It can be written as a small tag inside the page, or as a hidden HTTP header called X-Robots-Tag.

HTTPS

HTTPS is like sending your site's traffic in a sealed envelope instead of on an open postcard: the connection is encrypted, so it cannot easily be read along the way. It is expected for almost all sites today.

Page speed and Core Web Vitals

Core Web Vitals are three simple report-card scores for how a page feels to use: how fast it loads (called LCP), how fast it reacts to a click (called INP), and how much it jumps around while loading (called CLS). A free tool called PageSpeed Insights checks all three for you.

Mobile-friendly

Most people search from a phone, not a computer. A mobile-friendly page is one that still works well on that small screen: text you can read and buttons you can tap without zooming in.