I'll start with a simple question: have you ever thought that linking to your Twitter profile can be very difficult? Probably your answer is "not really!", and in this case maybe you could find what I'm going to show you useful.

But let's start from the beginning...

A while ago I was re-reading a post by Kristi Hines on SEOgadget about using your Twitter profile for your link building: I had bookmarked it since it contained good and immediate tips to build links just having a Twitter Profile, but in all this months I had forgotten to put them into practice. However, working on it, I also thought that while building links to your website, with those resources you indirectly build links to your Twitter Profile, so you would aspect an important impact on your personal branding management too, particularly for you name/nickname SERP. Is it so? Yes, in most cases it is, but the are some problems. Twitter's bad search engine optimization, third-party links, and our own mistakes, in fact often make our link building less effective than it could be.

Let's search on Google [Kristi Hines], for example. Kristi is a very well know professional and there are a lot of reference for her name, however her Twitter profile ranks well and helps her personal branding:

I'm not as important as her, but if I search for my name on Google.it (I'm Italian) there's no trace of my Twitter profile (@zen2seo), even if it's linked in several articles and in my Google+ profile. It only appears in the fourth page of results.

I asked myself why, and found something interesting. Just look at the two screenshots and you can find one of the issues I was talking about: my URL contains the escaped fragment (#!), Kristi's doesn't. So, simply, Twitter is duplicating its pages, with a dilution of their strength, and Google is indexing different versions of the same content.

How many times? I've spotted a lot of variations and only a few certain conclusions. To better understand this confusing situation, let's check the most common causes of duplication of a website.

1) www vs. non-www

If you search for a www version of you profile, you won't find any results:

This is because www URLs are 301-redirected to the non-www ones:

So, our first conclusion, for now, is that you should link to the non-www version.

2) http vs. https

Using few advanced search operators, the first duplication I've found comes from http/https URLs versions.

As you can see, Google is indexing both http and https versions of the site. Which one would be better to link to? It's too early to answer to this question, but I'll try to give you some suggestions in this post.

3) The @ sign

Since we commonly refer to our Twitter Profile using the @ sign (es. @Zen2Seo), I wondered if I was able to find URLs containing it. I haven't found this duplication for me, but it exists in other cases.

4) Slash vs. non-slash

As for the previous case, I've found some duplicated URLs ending with the slash ("/")

5) Capital letters

My nickname is Zen2Seo, with a capital Z and S, but in the first screenshot you can see only lowercase letters. Does Twitter handle this difference properly? Not so much. A little deeper query shows you can have also capital letters indexed.

6) Third level subdomains

It's quite easy to notice that Twitter duplicates its pages (at least statuses) on several subdomains. I stopped checking after I found EN, IT, ES, DE, FR, and each of them is affected by the same problems we've already exposed.

7) IP Address

As you've seen there are several causes of duplication (and you can combine them too as you want), but moreover I've found Twitter is duplicating its content also via IP address:

What's your "canonical" Twitter Profile?

In this huge URL confusion, you should be a (good?) SEO to understand what is the right URL to link to. But the majority of the people that use Twitter are not aware of this kind of issues. And Twitter doesn't help them at all.

Remember Kristi's URL and mine: Twitter use AJAX and URLs with the escaped fragment, so the average webmaster has another choice (better, another combination parameter) and since the actual URL of the browser shows the /#!/ part, many people link to it.

In this case, things are far more complex than the previous situations. Vanessa Fox's interesting post about Twitter infrastructure issues shows how Twitter redirects the "normal" URL to the escaped one with a 302 redirect; here search engines crawl twitter.com/?_escaped_fragment_=/YOURNICKNAME and receive a 301 redirect to http://twitter.com/YOURNICKNAME.

I bet this is confusing for some SEOs too, but - without investigating more - we can conclude that Twitter needs AJAX URLs but probably they want the HTML URL to be indexed, so we should link to it. This consideration becomes quite a certainty since they've recently announced they're getting rid of the hashbang (but just because they want to give users more speed not because of SEO issues...)

Another hint comes from Twitter trying to canonicalize URLs via canonical link tag

As you can see, they choose as canonical URL the one with:

• https
• non-www
• no "at" sign (@)
• minuscule letters
• no slash at the end
• no hashbang (/#!/)

The previous screenshots, however, demonstrate Twitter isn't succeeding with canonicalization, so if we link to a wrong profile URL we can aspect that link won't help us in our personal (or brand) reputation management.

Of course if you are as known as Rand Fishkin, you don't have to worry about your Twitter profile appearing in the SERPs for your name/brand. But if you aren't, something like this could pretty well be a problem:

So, how must we link? You could link to your canonical URL but at the moment, with Twitter unable to solve its duplications, maybe this is not a universal suggestion. I think it could make sense to choose looking at what Google prefers in its SERPs and it can be different from case to case.

So, check your ranking URL and link well!

Now, before you go, just a final note: if you've appreciated my SEOMoz post, feel free to follow my Twitter profile (zen2seo) or visit my SEO blog. Clearly, I expect a lot of new followers now than I'm linking to my "right" Twitter profile URL! ;)