https://www.semrush.com/blog/technical-seo-audit/

Semrush’s Site Audit Tool

robots.txt

Sitemap
An HTML sitemap is written so people can understand a site’s architecture and easily find pages.
An XML sitemap is specifically for search engines: It guides the spider so the search engine can crawl a website properly.
site:domain.com inurl:sitemap
site:domain.com filetype:xml
site:domain.com ext:xml

Subdomains
site:domain.com -www

Indexed Versus Submitted Pages
site:domain.com
or
site:www.domain.com

Site Structure
Site structure is how a website is organized. “A good site structure groups content and makes pages easy to reach in as few clicks as possible.” It’s logical and easily expanded as the website grows. Six signs of a well-planned and structured website:

It takes only a few clicks (ideally three) for a user to find the page they want from the homepage.

Navigation menus make sense and improve the user experience.

Pages and content are grouped topically and in a logical way.

URL structures are consistent.

Each page shows breadcrumbs. You have a few types of breadcrumbs to choose from, but the point is to help website users see how they’ve navigated to the page they’re on.

Internal links help users make their way through the site in an organic way.

It’s harder to navigate a site with messy architecture. Conversely, when a website is structured well and uses the elements listed above, both your users and SEO efforts benefit.

3. How To Audit Canonical Tags and Correct Issues

4. How To Fix Internal Linking Issues on Your Site

Your site has two primary types of internal links:
Navigational: Often found in the header, footer, or sidebar
Contextual: Included within the content of the page