What is a trackback? What are trackbacks used for? Why should you care?

A few people have asked me to explain Trackbacks. I can understand the confusion, it is one of those things people assume you just know about.
Many people spot the “Allow pingbacks & trackbacks” question in their WordPress posting screen that seems to be important somehow but has no explanation.
What is a Trackback?
Trackbacks are ways for one site to notify another about an update.
SixApart, the people behind Typepad and MovableType, invented Trackbacks as a way for blogs to inform another when it has been referenced in a post.
A trackback consists of a link and optionally a snippet of text. On many blogs, you do not even have to enable trackbacks.
Just like comments the trackbacks are moderated because unscrupulous spammers have abused them in the past.
How Trackbacks Work
Here is how it normally works:
- Mary writes an article on cheese.
- Joe Blogger writes about Mary’s new post saying it is really cool.
- Joe’s blog sends a trackback to Mary’s blog.
- Mary’s blog receives the trackback and Mary sees the trackback in her comments moderation area.
For most people this is all automatic and under the hood, you just link to a post and it is all handled for you. In others, you have to send trackbacks manually.
So why bother? What is trackback and blog pinging useful for?
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Why Use Trackbacks
Trackbacks are like a kind of commenting but using your blog post instead of posting a comment over at the other person’s comment area.
You are saying “I have written about your post over on my blog“.
The hope would be that the referenced blogger would notice. An additional benefit is if the trackback gets published that people might click through to read what you have to say.
Many trackback links are wrapped in “no-follow” condoms so the SEO value is nerfed, but in some cases, you might still get a clean link.
Why You Don’t See Blog Trackbacks Today
While useful in the past for cross-blog communication and reactions, published trackbacks are not really very common any longer. Due to spammer abuse, the feature is now very often disabled entirely.