With a permanent redirect, HTTP status code 301, you sends users to a new URL when they try to get to the old one. The permanent redirect is SEO-superior to the other redirects like the temporary (302) redirect, as it passes most of the link equity to the target page and allows search engines to update their index. 301s also pass relevancy signals to the target page.
301 redirects do reduce net relevance (since some content is removed and link signals are dampened) but may improve relevance of target page if the redirected page was relevant to the target.
Tip 1: Avoid unhelpful blanket redirects of a ton of URLs to single page like the main blog page or a home page when they should go to several specific URLs.
Such redirects are no better than 404s for UX (worse, in my opinion). They are frowned upon by Google, which is getting better at giving unhelpful redirects the SEO benefit (or lack thereof) they deserve; consider their rally against “faulty redirects” for mobile. Blanket 301s are yesterday’s SEO tactic – good SEOs just don’t do it anymore, but bad SEOs still love ’em.
Tip 2: Avoid redirects that make the user ask “WTF?”
One sloppy redirect is a long chain of redirects that slow down page load time (especially bad for mobile). Other sloppy redirects include the redirect loop, accidentally redirecting the wrong URL, and accidentally redirecting tothe wrong URL. Such issues are common with large, complicated webs of redirects and can be caused not only by carelessness, but also by ignorance or confusion of the technical implementation setup.
Tip 3: Tell users what is happening (when appropriate).
Some open communication to redirects can improve UX. For example, you could add a note explaining which old posts (on a blog) or which discontinued products (on an ecommerce site) have been redirected to another page, and why.
Tip 4: If you’re confused at this point, here’s a friendly guide on redirects and some info on technical specifics.
Summary: 301 redirects have long been a favorite weapon of SEOs as they are a way to pass link juice from an old page that isn’t taking advantage of it to a page that needs and deserves that link juice. However, don’t use 301s carelessly. Only use redirects when it actually improves the user-experience, for example when you can say “hey I have a much better post on this exact topic”. Only use redirects if you will commit to doing them right