Missing People is hoping to track down missing children using Twitter, as well as raise awareness of its new missing people phone line.
As part of International Missing Children’s Day the charity will tweet an appeal every 30 minutes for 24 hours and encourage its followers to retweet.
The Big Tweet, as it is being called, also coincides with the launch of the charity's new hotline that people can phone and text when someone goes missing - 116 000 - and all the tweets on the day will include the hashtag #116000.
It is the second time the charity has run the online event and last year its tweets about missing children were retweeted more than 7,000 times with 15,000 people clicking through to the appeal pages.
However, the charity could not tell civilsociety.co.uk whether the campaign successfully found any missing kids.
Stephen Fry, a Missing People Patron and early adopter of Twitter, is supporting the appeal again.
The day will also see the launch of a new Missing Kids website, which the charity has worked in partnership with the Child Exploitation and Online Protection Centre and the charity Parents of Abused Children to develop. It brings together online information about missing children and information about keeping children safe on the internet.