Is there any problem with circular permanent redirects?

Question

In e-commerce websites, we want to include product title in the URL for SEO benefit... however the title is not unique so we generally include an id along with the title.

The title is determined by the user, so they may change it to anything they want...

This is exactly the same situation that happens in stackoverflow, as descrived below:

---

The question link structure on stackoverflow is:

https://stackoverflow.com/questions/id/comma-separated-title

For example:

The correct URL: https://stackoverflow.com/questions/73793686/building-a-custom-canonical-url-in-python

If I change the URL to: https://stackoverflow.com/questions/73793686/building-a-custom-canonical-url-in-python-java

I will get a permanent redirect to the correct link.

Now I go ahead and change the question title in stackoverflow:

This time if I send a request for:

https://stackoverflow.com/questions/73793686/building-a-custom-canonical-url-in-python

I will get redirected to:

https://stackoverflow.com/questions/73793686/building-a-custom-canonical-url-in-python-java

---

I want to follow the above approach in my e-commerce website (for SEO purposes) however I am not sure if there is any issue with having circular permanent redirects, like above?

---

How is it circular?

Originally I told Search engines

.../building-a-custom-canonical-url-in-python

should be redirected to:

.../building-a-custom-canonical-url-in-python-java

Now I am telling the search engines that:

.../building-a-custom-canonical-url-in-python-java

should be redirected to:

.../building-a-custom-canonical-url-in-python

So if the router/search engine/browser remembers my instruction, this could end up in an infinite loop... it practice it does not.

But is there any issue with the above approach? One can argue that we are misguiding the routers by giving them contradictory instructions.

Answer 1

BNazaruk's answer covers the SEO side of things; I want to address the browser side.

When web browsers sense that their cached 301 would cause a circular redirect, they invalidate their cache and re-fetch the redirected URL anew. So, cached redirects cannot cause circular redirection in modern mainstream web browsers.

Basically, not only is there no SEO issue with the redirect pattern you described, but there's no browser issue either. It's a perfectly fine pattern to use.

Answer 2

The redirect is not circular because even though the 301 is defined as permanent, there's very few permanent things on the web and Google recognizes it.

In short, Google reindexes permanent redirects to make sure they're still there. The frequency of that reindexing is a subject to quite complex logic whose aim is to avoid overloading the indexer while still allowing to keep essential pages perfectly indexed. In case of normal sites and not benchmark-class sites like SO, the frequency most often depends on backlinks to the 301 url.

Even without purposeful/forced reindexing, when the indexer Sees that A -> B first time, it may stop visiting A, but start visiting B. After it, when the indexer sees that now B -> A, it will definitely follow the redirection and reindex the A, updating its record in the DB, changing its status from 301 to 200.

No harm done, no perceived circular redirections.