n case you have ‘page not found’ error rel canonical will allow indexing of the page during repairs or redesigning of web pages. Search engines following a heuristic approach to find the canonical in case of a 404 error. You should follow the rules as you use rel canonical for relative paths and search engine processes your website in a regular format.

301 redirects means the content has moved permanently to this new location. Google suggests that when your site is shifted to a new domain, two sites are linked to each other. Apart from this, you can also use this redirects system for bringing multiple page browsers to the same content page of a website.