Once you've started using Twitter, it won't take long before you come across what's known as a hash tag. That's when you see something in a tweet that has a # prefix. (The # is a hash symbol, hence the term hash tag or hashtag.)
For example, if you've seen tweets related to the recent U.S. government stimulus bill, you may have noticed some of them had #stimulus in them.
It took me a while to wrap my head around what the purpose of this thing was but, once I "got it," I realized it's not as complicated as it seems.
A hash tag is simply a way for people to search for tweets that have a common topic. For example, if you search on #LOST (or #Lost or #lost, because it's not case-sensitive), you'll get a list of tweets related to the TV show. What you won't get are tweets that say "I lost my wallet yesterday" because "lost" isn't preceded by the hash tag.

The good thing about the hash tag is that if someone wrote a tweet without putting the word LOST in the main message, it will still show up in your search because of the tag. Eg. "Who is hotter? Jack, Sawyer, or Desmond? #lost"
The flip side is that if you search using the tag, and someone wrote a tweet about the show without including it, that tweet won't show up in your results, even if LOST appears in the text. Eg. "Do you think LOST has jumped the shark?"
In a way, hash tags allow you to create communities of people interested in the same topic by making it easier for them to find and share info related to it.
Where do hash tags come from?
I think this question gets to the heart of the confusion about these danged things, because hash tags are NOT any kind of official Twitter function. The company has not created a list of topics that we can browse through to see if there's one that interests us.
So where DO they come from? Well, any user can create one simply by adding it to their own tweet. For example, when the plane went down in the Hudson River a couple of weeks ago, some Twitter user wrote a post and added #flight1549 to it. I have no idea who this person was, but somebody else would have read it and when he posted something about the incident, added #flight1549 to HIS tweet. For something like this, where tweets would have been flying fast and furiously, it wouldn't have taken long for this hash tag to go viral and suddenly thousands of people posting about it would have added it to their tweets as well. Then, if you wanted info on the situation, you could do a search on "#flight1549" and see everything that people had written about it.

As you can see, it's a very organic process that works simply because of a group mindset that people like to categorize topics and this is one way to make it easier to do so.
How do I track topics of interest to me?
Let's say I'm interested in basket weaving. The first thing I would do is a basic Twitter search on the term itself so I can see if someone's already created a related hash tag.

Now, I've gone through a few pages of results and, while there are plenty of tweets with the term "basket weaving" in them, I'm not finding any that have included a hash tag.
So now if I want to create a community of people who will share their love of basket weaving, I'll create my own hash tag.
Note: Before you create your own tag, you might want to search on a few variations to make sure they don't already exist. I looked for #basketweaving, #basket, and #weaving, and they either didn't exist or didn't apply to this topic.
Since the tag will use up some of my 140-character limit, I want to keep it fairly short, while still making it precise. For example, #basket might make some people think of basketball instead of basket weaving. So I could create a tag called #basketweave that isn't too long, but is clear what it's about.
To make this hash tag "live", all I need to do is write a tweet and add #basketweave to it. It can be anywhere in the tweet, not just at the end. And I would probably announce that I was creating it to alert my followers. For example:
Fellow basket weavers. Let's share tips and tricks by adding #basketweave to our tweets.
Now, I'm not going to do that, because I'm not actually interested in basket weaving. (No offense to any weavers out there.) However, I have just created a new hash tag called #tech4ludds for any tweets that people want to associate with Tech for Luddites. I did it by posting this:
Starting a new hash tag for Tech for Luddites. Got a question for me or a great tech tip to share? Add this to your tweet. #tech4ludds
This way, I'm letting my followers know that this now exists, so they can add the hash tag to their own tweets if they think it's related to this blog somehow.
(I actually wanted to create a tag for t4l for brevity but there was already one tweet in existence using that tag, if you can believe it! It's in Dutch and has a link to the Netherlands Unicef site. A Google search leads me to believe it stands for Time for Learning. Probably a great program but still... Bummer.)
Now, if I search on #tech4ludds, I'll only find that first tweet I wrote. Fingers crossed it doesn't stay that way!
I hope the above clarifies the Twitter hash tag, which I know can be very confusing to new Twitterers. If you still have questions about it, please send me an e-mail at F1@TechForLuddites.com.


















{ 29 comments… read them below or add one }
Thanks for this - you probably covered over twitter thingy somewhere - but I've seen RT a lot on twitter today and understand it's used to show a repeated message - but don't quite understand its use. Do I type it in myself or is their a function I'm missing?
Thanks!
Diane
Hi Diane.
Yes, a retweet is a way to "forward" someone else's tweet to your own group of followers. Twitter doesn't have a built-in option for them. You have to manually add in the RT before the tweet and include the username of the person who wrote it orignally (with the @ sign in front of it), to give him or her credit. I wrote more about retweets in this post, Four Ways To Engage Your Tweeps.
Some third-party apps, like TweetDeck, do have a function that automatically adds in the retweet code. Here's a post about how to use TweetDeck as well.
Thanks for your comment and question!
Elizabeth,
Thank you, thank you, for your most helpful posts about twitter. I'm taking full advantage!
Jill
Thanks for your comment Jill. I'm glad you're finding my posts helpful!
I recently started a new group/hashtag, and I tried searching for it so I could find the rest of the people tweeting on this specific subject, but my hashtag isn't coming up in a search. I know for a fact there are at least 20 people using it throughout today for this discussion, though. How do I find them?
Elizabeth:
Very helpful, luddite-level briefing on the hash tag. My only question is about how to "follow" a hash tag without using Twitter search. Is that possible?
Thanks.
Jim
Hi Jim.
Thanks for your question. I wrote a post about following hash tags after this one. The first three options all require doing a Twitter search once but then you don't need to do it again afterwards, so I don't know if that addresses your concern. The fourth one doesn't require you doing the search through Twitter yourself, but I assume it's using the same engine behind the scenes.
Let me know if this solves your problem.
Elizabeth
How about those groups who abuse the hash tags (or at least it seems like they do) when they @usernamer1 @username2 etc but contribute nothing to a conversation--is there an etiquette post about this somewhere?
Good question, Ark Lady. I haven't written a post about that before, but it's a great idea for a topic. So thanks for the suggestion!
Nice post.
Thanks Sharad!
It seems like sometimes the hash-tagged word/phrase becomes a hotlink and other times not. What's that about?
thanks
That's a good point, Louis. One I hadn't noticed before. It seems like on your main Twitter page, the hash tags don't become links. But if you do a search on a hash tag, then they are links on the results page. TweetDeck also automatically turns them into links that run a search on the term. It would be a good idea if Twitter made them links in people's main streams as well.
Are there other places you're referring to that I haven't addressed?
Twitter trending topics, search and related applicatins thrive on these hashtags, as they serve as noted keywords in the sea of tweets going through the microblogging platform. So determining the perfect hashtag is akin to creating the perfect title for a blog post.
http://www.pupuweb.com/blog/promote-yourself-with-twitter-hashtag/
Great post on hashtags and I still see it being referenced on twitter as a resource for new twitter users.
Since the post several websites have launched making hashtags easier to watch and tweet about. Hashtag definition websites have also been popular over the recent months.
If you frequently use hashtags check out http://wthashtag.com for number of free tools.
Thanks for the clarification.
That was great now I get it and will create one now. @healinginvest mikeb360.com
Hi, I'm having trouble with hashtags. I've saved a couple of searches of interest but even though I use the #whatevername, it just doesn't work. I've tried this quite a few times, even copied and pasted just in case there was a secret trick I didn't know about, still nothing. Help!
Hi Suzie. This is a fairly common problem. This post has more information including a solution that has worked for several of my other readers. Hope it helps:
http://www.techforluddites.com/2009/08/quicktip-when-you-or-your-hash-tags-dont-show-up-in-a-twitter-search.html
Thanks Elizabeth for the quick response. I will try it all until it works. :)
I get it now!
Thank you so much!
This is going to make searching and growing my network SO much easier!!
I'm glad it helped!
What I need to know is, how can I follow some trend with a particular hash tag? I'm not interested in creating my own. Thanks.
Hi Thomas.
This post may help you:
http://www.techforluddites.com/2009/04/reader-question-keeping-track-of-twitter-hash-tags.html
Thanks.
Thanks for your article on hash tag in twitter.
Thanks, that was really well explained. I didn't realise it simply made use of the default Twitter service. Cheers
Very clear. This hash tag issue has been bugging me for sometime. You have explained it very well. Thanks buddy.
Thanx a ton !!!