A hashtag is a word or a phrase prefixed with the symbol #. It is a form of metadata tag. Short messages on microblogging and social networking services such as Twitter, Tout, identi.ca, Tumblr, Instagram, Flickr, Google+ or Facebook may be tagged by putting “#” before important words, as in:
#Wikipedia is an #encyclopedia that anyone can edit.
Hashtags provide a means of grouping such messages, since one can search for the hashtag and get the set of messages that contain it.
Facebook hashtag(recently introduced by facebook)
Basic Hashtag information:
Click on the hashtag to get redirected to its feed. You can also click on hashtags that originate on other services, such as Instagram.
Every hashtag on Facebook has its own unique URL.
Search for a specific hashtag from your search bar, for example, #NBAFinals or type facebook.com/hashtag/xxx into your browser (replace the x’s with the tag you want to look up).
Compose posts directly from the hashtag feed and search results.
A few #HashtagTips
Marketers are already embracing the power of hashtags and coming up with ways they can be used to their highest potential. You can find some great tips and ideas under #hashtagtips including:
Whether you have the new #hashtag feature or not, start using strategic hashtags in your public Facebook posts (profile and page). Everyone who has the feature will see your hashtags as clickable links.
Each hashtag on Facebook has its own unique URL with a status update box at the top. Drive traffic to that URL from other sites to spark more conversation.
Include hashtags even when posting on mobile. Although hashtags don’t work on mobile (yet!), they do work on desktop when posted through your mobile device.
Use #hashtags to start a conversation with a group. Every word you make into a hashtag will be grouped into its own status update box!
Think about your industry and target market, and the types of hashtags you use on other social networks.
Use tags in trending topics related to your industry.
Capitalize the #FirstLetterInEachWord of your hashtag to make it more readable.
Don´t overdo your post with hashtags, 1 – 2 is more than enough.
What about hashtag privacy?
You control who sees your posts, including those with hashtags. Facebook marketing expert Mari Smith summed up all the hashtag related privacy settings as follows:
As with all personal profile features on Facebook,privacy settings prevail.
If you publish a post on your profile to friends only, and the post contains a hashtag, the hashtag will be clickable and open up to display all other posts on Facebook containing that hashtag.
But, ONLY friends can see friends-only posts that show up in hashtag searches.
Public posts—with or without hashtags—are public.
Private (friends-only) posts—with or without hashtags—are just that: private and visible to friends only.
Even when friends include hashtags in comments on your friends-only thread, your post is still private and visible just to your friends.
With hashtags shared in private groups, that clickable hashtag will open to show public posts with that tag (along with any friends’ posts with that tag), but posts from the private group are only available to group members.
Individual comments on threads do not surface in hashtag searches.
for some reason, Instagram also bans these 10 inoffensive hashtags:
#iphone4s (#iphone5 is not banned from searches)
so avoid these hashtag in your instagram post.
To get complete list of banned instagram hashtags head over to Nick Drewe’s site The Data Pack that listed a bunch of banned words.