What Is Trackback?

Sometimes when you see a post on somebody's blog that you like, it's enough just to leave a comment on the other blog about that issue. But what if you've got something to say about the issue that you'd like to share with readers of your own blog? If you do post to your blog, you have to go and leave a comment in the other blog if you want the people there to know about your own blog entry.

This is where trackback comes in. Using trackback, you can automatically notify another blog about your new entry and a link to your entry will appear in that blog's list of trackback pings. Now visitors to the other blog will be able to come to your blog.

In order to send the trackback notification to another blog you will need to have a trackback ping URL for the entry you want to comment on. There are several ways of getting this:

1. The "Trackbacks" pop-up or the individual entry page at that site will generally list a URL to ping. When you go into MT to post, you should see a field called "URLs to ping". Copy the URL that you found earlier into this field. The ping will be sent when you save your entry
2. Use your MT bookmarklet to post your entry while viewing the other blog. If you are at an index page, you can use a drop-down menu in your bookmarklet to select which entry on the index page that you want to ping. If you are looking at an individual entry page, the URL for that entry will be listed in your bookmarklet with a checkbox. Select what you want to ping and the ping will be sent when you save
3. You can set up your Blog Config preferences to use auto-discovery. This means that whenever you include any URL in the body of your post, auto-discovery will visit that URL and determine if it contains any blog entries that can be pinged. If so, pings will be sent when you save. This is by far the easiest method, since you don't have to think about it or do anything

At this time, only some blogging systems are configured "out of the box" to use trackback, primarily Movable Type (others include Bloxsom and Blojsom, Nucleus, b2, and Radio Userland). However, if you have your own web server space you may be able to set up Stand-Alone Trackback to work with your blogging system. If you don't have your own web server space, try No-Host Trackback or use the Simpletracks form. People who use Haloscan for comments can now receive and send trackbacks. If you are a Haloscan user, you can use this form to send trackbacks (any other form, such as Simpletracks, will also work for this purpose). You might also wish to look into similar applications such as Pingback.

The implementation of trackback that I described above is basically one-to-one, a way of linking between two individual blog posts. In that sense, it's like a remote commenting system.

Trackback can also be used to create content repositories, for instance a collection of recipes or book reviews from many different bloggers. MT can be set up to allow trackback pings to categories in a blog as well as to individual entries. If you wish to ping somebody else's category there are two ways of doing it:

1. If you just want to post an occasional entry on that topic, you can find the category trackback URL from the target page and enter it into the "URLs to ping" field like you would with an individual entry's trackback URL
2. If you expect to post frequently on this topic and wish all your entries to show up in the repository, you can configure one of your categories so that any time an entry is posted to that category, it pings a trackback URL. Grab the category trackback URL for the target site and enter it in your category configuration page. This is the easier of the two methods since once you've set it up, you don't need to think about it again

This is not a complete list by any means but should be enough to help you get started.

• BlogPopuli - if you're blogging about blogging, send it here
• Book Review Repository - submit your book reviews
• KMPings - repository for posts about knowledge management
• Lazy Web - a wish list of blogging tricks that people would like to see developed; developers read it for ideas
• The Red Kitchen - submit your recipe posts

There's also The Internet Topic Exchange, which allows you to set up your own trackback repository on any topic that you choose (this is better than setting up your own categories as repositories since you can ping it yourself).

If you know of any trackback repository that's not listed here, with its web address and I'll add it.

Here are some unusual uses of trackback:

• Display songs recently played on WinAmp (get really creative, remove old pings, do it from iTunes)
• Mobile blogging with trackback

Another interesting use of trackback is Memigo, a site that collects news articles and allows users to rate them. You can tell Memigo to check your RSS feed for links to news articles that you've posted about. If Memigo finds a good one, it will send you a trackback ping. The whole idea of trackback is to allow readers of your blog to find additional resources elsewhere that are related to your blog entry. With the trackback ping from Memigo, your readers can now visit the Memigo site and look for related articles in the Memigo database. This is a great new use of trackback!

A slightly more complicated use of trackback (which requires installing the stand-alone trackback program on your web server) is aggregating the comments you make on other sites. Once you have this set up, you ping your blog with information about each comment you make elsewhere. Then readers of your blog can see what else you're saying.