This is a continuation of the question: How to handle canonical url changes like Stack Overflow.

Say I have the canon url:

questions/11/car <---canonically-linked-from--- questions/11/

What will happen if I want to change the canon url to

questions/11/car-with-sgx

Obviously, questions/11/ will point to the new canon url.

But how should the old questions/11/car change to the new one? There are two ways:

1. 301 redirect that to new canon url
2. the old canon url canonically link to the new canon url

According to this post:

[By using canonical link instead of redirect,] OldPage.html’s rankings will drop over time due to fewer internal links, but the canonical tag won’t make it disappear entirely. It could theoretically remain in their index until one of the following occurs:

1. it is redirected permanently via 301
2. it returns a 404 for an extended period of time (they will keep checking for a while before dropping a URL)
3. a meta robots “noindex” tag is added

If this is true, I really need to use redirect from old canon url to the new canon url, which means I need to keep a log of previous old canon urls of this content, so I know when I can redirect. This is a bit of a hassle to do.