If you'd only like the content to live at one location, and you're worried about legacy links that people shared across the internet breaking, then a 301 redirect from the old URLs to the new URLs is what you're looking for.

Every HTTP Request receives a response code from the web server. Response codes in the 200s mean "everything went well", response codes in the 400s mean "user error" (like the famous 404, "we couldn't find the page you requested") and response codes in the 500s mean server error (Twitter's famous 503 Fail Whale).

300s indicate some sort of redirection and a 301 response code specifically tells the requesting client that this piece of content has moved to a new URL *permanently* and will never be back at this old URL.

When web browsers receive a 301 redirect, they'll cache it and automatically forward all future requests for the old URL to the new one without even asking the server. Similarly, when search engine crawlers encounter a 301 redirect for a URL that they had already indexed, they update their information to move that old content (and all of it's old ranking information) to the new URL. This means you don't have to "start over" to get a piece of content to rank if you move its URL.

However, your question makes it sound like you actually *do* want the exact same content to be served out of multiple URLs, but you'd ideally like only one copy of that content to be indexed and ranked to avoid splitting your inbound links and any other duplicate content issues.

In that case, I'd check out adding so called "rel-canonical" tags to your pages, to indicate which version is the "canonical" version of that piece of content, and have all other versions point to the canonical one with the tag. Google is pretty good about using these, and Bing says they use it has a "hint." More info:

https://support.google.com/webmasters/answer/139394?hl=en

In a world where websites might choose to organize the exact same content in a number of different ways, adding "rel canonical" tags to your pages adds a lot of semantic meaning and helps you avoid a number of issues that duplicate content brings. Hope that helps!

I'm with Hartley on this one. But it all depends on your content.

If you are going to have (and maintain duplicate content on all of these URL's) the the re-directs from the old URL's to the new URL's only take care of half of your problem, you still will be cannibalizing the rankings of these pages as they will be ''dinged' for duplicate content (worst case scenario) or at the very least, search engines will not know which version is to be representative, will not be able to discern any difference, and instead of trying to figure out which version should rank higher, both will receive a lower relevancy score. This is where the rel=canonical tag comes into play - which essentially tells Google, "hey, this is the representative version of this content that I want indexed," and to implement this you would need to add the <link rel="canonical" href="final destination URL goes here" /> to every URL that has duplicate content, all pointing back to the "champion" version.

Whenever you change URL's, that you wish to remain indexed you must do a 301 redirect for continuity of both page-level authority and so users/crawlers can make it to the correct final destination.

There are few ways to do it:

1. 404 :- This will be too bad
2. 301: You can do this but as you have huge number of url, doing this will also not be a good approach
3.Canonical: This will be best way in your case, along with you should also do no-index and no-follow for all these pages

I would do 301 redirects for the unwanted urls for a couple of months and then 404 then. This would require more work but it'll give you less impact in search ranking and traffic.

404 is too bad for SEO but it might impact your traffic.

Simple questions, simple answers.

Clearly a 301 redirect case because there is no canonical value for just switching URLs...however...this is the most important line on this whole thread coming up...

You have to do a search in Google to see which pages are ranking better based on URL and keep those to have maximum ROI. To do this properly requires a rank checker and keyword list to see how the URLs rank.

Should be a snap for a SEO specialist with Screaming Frog and a proper rank checker -- at least to identify the right URLs to keep. Now, updating the URLs with a 301 redirect should probably be done in programmatic fashion to save time...

Cheers --
Nick

The best answer i could suggest is Rel canonical.