Handle canonical when multiple document revisions are available?

Question

On my page I'm making all versions of the manual of my project available:

• https://example.com/manual/0.10/index.html
• https://example.com/manual/0.11/index.html
• …
• https://example.com/manual/0.22/index.html
• https://example.com/manual/latest/index.html

Handling the latest is simple as it's a symlink on the server to the latest version 0.22 and when the 0.22 manual is containing HTML elements like

 <link rel="canonical" href="https://example.com/manual/0.22/index.html" />

everything should be fine for Google et al SEO.

But what happens when parts of the manual are containing (nearly) the same content during different versions as e.g. the project didn't change on those places?

My guess is that Google will punish these pages as they are looking like duplicated content.

So how can I tell the search engines that this duplicate content is fine in this case?

(Note: This solution should be something that is static as I don't want to regenerate old manuals just because I add a new version to the list)

Answer 1

My guess is that Google will punish these pages as they are looking like duplicated content...

Google does often give pages with duplicate content less weight in SERPs, or even choose not to index them. However, that word "punish" is quite misleading because it suggests some sort of dark mark or SEO penalty on your site, which couldn't be further from the truth (see The myth of the duplicate content penalty).

But what happens when parts of the manual are containing (nearly) the same content during different versions as e.g. the project didn't change on those places?

I would be surprised if Google doesn't have a special rule to find what looks like version numbers in the URL structure, then take that into account when indexing. I might consider just trying it out and seeing what happens. You won't get into any trouble, as again, Google's duplicate content detection is just an indexing rule and does not trigger any kind of penalty. It's possible that Google's algorithm is smarter than you give it credit for.

how can I tell the search engines that this duplicate content is fine in this case?

The question isn't whether the duplicate content is "fine" or not, it's always "fine" to have duplicate content on your site if it serves a purpose. Google may choose not to index your previous manual versions, which is fine. They may choose to index the previous and current versions, which would be ideal. If they index only your old manual versions and not your latest version, that's when I would look into supplying canonical tags.

In short, the best way to figure this out is to just try it. You have nothing to lose.