Additional categories that you have assigned to items with this plugin are basically secondary categories. The primary category is the original K2 category. You can only have one primary and multiple secondary categories.
Items will keep the URL structure of the primary category to prevent duplicated content.
Why this feature isn't already in the K2 core is beyond me.
Note: If you use Joomla 2.5, there is a chance that you can't see the additonal categories in the backend. However there is a fix in the support forum available.
sh404sef slows down your website. You can find proof all over the sh404sef forum and other places where people complained about their site becoming slower and slower due to an increase of SEF URLs in the database.
After uninstalling sh404sef, page load decreases from 7-8 seconds to 1-2 seconds are not uncommon.
The support is obviously overwhelmed by this since their typical response is to upgrade your host, turn cache on (as if people weren't turning cache on from the beginning) or other excuses. However they also offer you to get a refund if you want.
The difference between sh404sef and Loomlas own core SEF is that sh404sef builds URLs on first page visit and stores them in the database. Joomlas Core SEF doesn't store any SEF URLs in the database, but creates them on-the-fly, eliminating performance issues.
There is another SEF extension for Joomla that also creates SEF URLs on-the-fly. I have tried it and pages load as fast as with Joomla's Core SEF.
If Anything Digital, the company behind sh404sef wants to stay in business with their product, I highly recommend them to completly rewrite how sh404sef works. sh404sef could be much better with on-the-fly SEF URL creation. The best way to convince them or Yannick, the coder behind sh404sef, is to go to their forum and tell them.
Thanks for your message and for your concern for SEF extensions technology.
If you had a concern about speed and your server, you could have tried. But instead you wrote this text in our pre-sales forum, then cut and pasted it here as a review - without downloading sh404SEF and thus without trying. You actually didn't even pretend trying but only gave general comment on a technology vs another one. That's not really what I call a fair review of an extension!
As usual, there are pros and cons in each case. Storing urls in database allows many things that are not possible with the on-the-fly method, and this is why all SEF extensions use it.
We're very much concerned with speed of course, as very slow sites have a real SEO penalty.
But speed isn't a problem, even with busy sites. If you need proof, our own site has a lot of urls and runs pretty fast.
That said, we are not standing by, and we introduced last year features to not only make sh404SEF itself faster, but even speed up the Joomla site it's running on, by caching Joomla and other extensions database queries.
Now a final comment: you consider on-the-fly creation faster than store-to-database: where do you think elements of on-the-fly urls (article or category titles for instance) are coming from, if not from the database?
K2 produces for any items, tags multiple, in fact endless duplicated URLs.
For over a year people were desperately trying to get help from the developers, but they simply didn't respond.
You can read everything in this thread: http://getk2.org/community/New-to-K2-Ask-here-first/6472-K2-SEO-issue---Can-it-be-fixed
The developer responded though to a bad review about K2 addressing these SEO issues, but all he had to say is praising K2 for its SEO (although he apparently lacks some SEO knowledge himself because there are tons of things to optimize SEO-wise) and saying that these duplicated URLs are Joomlas fault. Later he said that these duplicated URLs can be resolved by
a) making menu items for each item (meaning hundreds of menu items for each tag)
2) install a third-party SEO component.
So basically he admitted that a K2 vanilla installation is not usable for production sites because of the horrific SEO issues.
Ironically a user later submitted a K2 core hack that apparently resolves those issues, but it has some side effects on other parts of K2.
Other components such as flexicontent prove that those issues can be resolved without installing a 3rd party SEO extension.
Support is horrific, the developer makes false claims and people are loosing traffic due to the mentioned SEO issues.
So unless you are willing to pay for an SEO extension, I strongy discourage anyone from using K2. But even then, hundreds and thousands of duplicated URLs will be stored in the database.
I highly recommend the developer to overthink his attitude and finally address those duplicated URL issues. And please, if you don't have a clue, ask other developers for help.
What you fail to understand is that K2 simply follows the Joomla! framework guidelines when it comes to URLs. For example, take this URL from a recent Joomla! announcement on joomla.org (it's the core Joomla! article system):
The URL is http://www.joomla.org/announcements/release-news/5471-joomla-3-0-2-released.html
But one can easily do this too:
Both URLs will render the same page of course. Now, this is not a bad thing SEO wise. SEO - which you fail to understand obviously - is not related in any way to how one or more users can manipulate a site's URLs. This is stupid if you think about it... SEO is about ordering/organizing a site's content so that search engines can pick up that content easily. The easiest the better for a site.
Anyone can read the URL you posted back to the K2 Community, but sorry, I'm not admitting anything.
As for the other claims...
a) "other extensions offer better URLs": if they are native extensions, no they don't
b) "K2 support is bad": define bad support for a free extension first. We're not elitists. If we were, we wouldn't have released K2, better yet, we wouldn't have launched a community.
You might wanna look for some other CMS perhaps. I strongly suggest Google's Blogger cause a) it's built by Google (= "beautiful" SEO for the paranoid ones) and b) it's free like K2.
Give us a break will ya?