Hashtags are a community-driven convention for adding additional context and metadata to your tweets. They're like tags on Flickr, only added inline to your post. You create a hashtag simply by prefixing a word with a hash symbol: #hashtag.
Hashtags were developed as a means to create "groupings" on Twitter, without having to change the basic service. The hash symbol is a convention borrowed primarily from IRC channels, and later from Jaiku's channels.
hashtags.org provides real-time tracking of Twitter hashtags. Opt-in by following @hashtags to have your hashtags tracked. Similarly, Twemes offers real-time tracking without the necessity of following a specific Twitter account. Also, with their purchase of Summize, Twitter itself now offers some support of hashtags at their search engine: http://search.twitter.com. Other services such as TweetChat, TweetGrid, and Twitterfall are also popular for following hashtags in real-time.
How To Use Hashtags
Start using hashtags in your tweets, preceding key words. It can be helpful to do a little research first, to find out if the subject you're tweeting already has an established hashtag. Also, check Suggestions and Tips and Example Uses below for ettiquette and general usage.
Finally, track other tweets on the subjects you're interested in (ie: those containing the appropriate hashtags) by browsing/searching at Hashtags.org, TwitterGroups, TweetChat, TweetGrid, Twitterfall, etc. You can set it up with RSS feeds as well.
Use of hashtags
Hashtags were popularized during the San Diego forest fires in 2007 when Nate Ritter used the hashtag "#sandiegofire" to identify his updates related to the disaster.
Chris Messina wrote up this use in his post on Twitter hashtags for emergency coordination and disaster relief.
Subsequent uses have emerged, especially alongside Twitter's track feature and the development of hashtags.org, which shows useful graphs of popularity and recency of hashtags. Another useful tool was the Terraminds twitter search engine that allowed for searching for arbitrary hashtags (search for #hashtag), but is now shut down.
Suggestions and tips
The use of hashtags is still an emergent phenomena, and as such, etiquette is negotiable, though some have already expressed their distaste for hashtags.
Used sparingly and respectfully, hashtags can provide useful context and cues for recall, as well as increased utility for the track feature. Used excessively can cause annoyance, confusion or frustration, and may lead people to stop following you. It's best to use hashtags explicitly when they're going to add value, rather than on every word in an update.
A good rule of thumb to follow is to focus on your update first, and only if it quantitatively adds value, to append one-three hashtags. There are no hard and fast rules, but Twitter should continue to be about answering the simple question: "What are you doing" rather than "What tags apply to what you're doing?"
When creating a hashtag for something that may consist of two or more words its a good idea to use the "CamelCase" format to maintain legibility. The idea is to join words with each words initial letter capitalized. For example if I wanted to create a hashtag for south Africa, I would type out: #SouthAfrica instead of #southafrica
- Events or conferences, e.g.: "Tara's presentation on communities was great! #barcampblock"
- Disasters: "#sandiegofire A shelter has opened up downtown for fire refugees."
- Memes: "My #themeword for 2008 is conduct."
- Context: "I can't believe anyone would design software like this! #microsoftoffice"
- Recall: "Buy some toilet paper. #todo"
- Quote: "Great minds discuss ideas. Average minds discuss events. Small minds discuss people." ~Eleanor Roosevelt #quote
(In rough chronological order)
- Twitter Hashtags: Nonprofits Speak Up by Devon Smith
- An Introduction to Twitter Hashtags on Wild Apricot Blog
- Carfi and Barnett on Support Tag Beacons by Stowe Boyd (Seminal post from 2006 on what would eventually be referred to as hashtags)
- Groups for Twitter or a Proposal for Twitter Tag Channels Felgi by Chris Messina (Discussing the use of the hash # character)
- Channels Will Improve the Twitter Experience by Brian Solis
- A question for Twitter users out there by Steven Hodson
- Twitter Hashtags: A Quickie by Stephanie Booth
- Twitter #Hashtags Backlash Begins by Stowe Boyd
- Twitter, TwitBox and hashtags by Steven Hodson
- Twitter Supports 'Tracking' But Not #Hashtags? by Stowe Boyd
- Tracking vs. Hashtags by Colby Palmer
- Twitter hashtags for emergency coordination and disaster relief by Chris Messina
- California Fire Followers Set Twitter Ablaze by Michael Calore, Wired
- Speaking at San Diego BarCamp 2007 by Nate Ritter (account of tweeting #sandiegofire information)
- What does # mean in a twitter post? All about octothorpetags. by Edward Vielmetti
- We’ve changed the way hashtags work by hashtags.org
- Tag Silo - Twitter Hashtags by Rod Edwards
- Making the most of hashtags by Chris Messina
- Hashtags.org by Stowe Boyd
- Making sense of Twitter by David Weinberger
- Hashtags for my Followees by Stephanie Booth
- Introduction to hashtag by Bwana
- Hashtagging Challenges When Events Occur at Different Times in Different Locations by Ontario Emperor (what the Rose Parade teaches us about hashtagging)
- Hashtags by Stephen Downes
- Twitter, Hashtag and 1 letter Taxonomy by Mahesh CR
- Why I Unfollow People Who Use Hashtags On Twitter by Dave Coustan (hashtags and "human" communication)
- Twitter needs better message tracking options by Emil Sit
- Learn with hashtags by Alexandre Solleiro
- Organizing Twitter with hashtags by Devon Campbell
- Live-tweeting an event? Set your hashtag UP FRONT! by Amy Gahran (when should an event hashtag be defined?
- How To: Use #Hashtags on Twitter by Montana Flynn
- Sponsored Hashtags by Adam Ostrow
- Studying Twitter and the Moldovan protests by Ethan Zuckerman.
- (empo-tymshft) #oow09 #hashtag emergence and standardization FTL by John E. Bredehoft (thoughts on adopting hashtags for events)
- The hash symbol has other uses, notably for denoting indices ("I'm #1!") or phone numbers ("Dude, what's your #?"). It's hard to avoid these kinds of collisions and they are simply something to consider modifying a common communication channel.
- Triple tags are not being parsed by some web services -e.g. #taxonomy:binomial=Alcedo_atthis is interpreted as being tagged simply "#taxonomy" by Summize and Twemes. Worse, HashTags simply renders the content as "#taxonomy", losing ":binomial=Alcedo_atthis" altogether. Twemes defend this on the grounds that triple tags are (were!) not covered in this spec, and claim a clash with colons as punctuation in casual conversation. The latter is bogus, as colons in conversation are generally followed by a space: as in this sentence. Also, plain-text sentences using a colon, followed by an equal sign, and preceded by a hash, and without spaces, #are:extremely=unlikely.
- Spamming of hashtags - what can be done when a bot network of porn spammers insert into a hashtag? (a weblog post talking about similar issue)
Hashtags may be defined (or their defintions found) using:
- HashDictionary (@hashdictionary)
- HashtagNation (@hashtagnation)
- What the Hashtag?! (@wthashtag)
- FollowFriday.es Spanish Twitter Ranking based on #followfriday recommendations.
- TweetChat Track hashtags in real-time
- Tweet of the Year Vote for the best Tweets of the year!
- LazyTweet Ask questions from the twitter crowd
- Tweetmapper Use hashtags to map your location
- Tweetag Aggregate tweets into topics and subtopics
- Twuoted All the #quote's on twitter.
- Twitter-Trends Aggregate German hashtags
- Hash-Dump Register the hashtags you've created and get credit for them.
- HashParty A twitter hashtag explorer that uses the Ident Engine to reveal the social graph profiles behind the tweets.
- Twimonial Let Twitter users use #twimonial to write a testimonial about a Twitter user
Hashtags are admittedly an early-adopter feature, but have been picked up by a number of folks. If you see folks making regular use of hashtags, feel free to point them out here:
- Alexandre Solleiro (als)
- Anthony Glyadchenko (antgly)
- Colby Palmer (colbypalmer)
- Dougal Campbell (dougal)
- Ear Ideas
- Chris Messina (factoryjoe)
- George Kao (georgekao)
- Glenn (justglenn)
- John E. Bredehoft (empoprises)
- Justin Kestelyn (oracletechnet)
- Kelvin (kelvin_lee)
- Kirk (mcmurrak)
- Nate Ritter (nateritter)
- Ontario Emperor (oemperor - replaced by John E. Bredehoft's empoprises account)
- Andy Mabbett (pigsonthewing) - also using triple tags
- Raines Cohen (raines)
- Stowe Boyd (stoweboyd)
- Montana Flynn (@montanaflynn)
- Scott Crider (CScottCrider)