Major technology companies are joining forces to spot terrorist propaganda and prevent it spreading online.

Twitter, Microsoft and Google-owned YouTube will join Facebook in creating a form of digital database to "fingerprint" flagged up terrorist content.

By collectively tracking that information, the companies said they could make sure a video posted on Twitter, for instance, did not appear later on Facebook.

Image: Facebook and its three main competitors will create a database

A joint statement said: "There is no place for content that promotes terrorism on our hosted consumer services.

"When alerted, we take swift action against this kind of content in accordance with our respective policies."


It went on to say the companies would share data "to help identify potential terrorist content on our respective hosted consumer platforms".

The joint statement did not say what type of technology would be used for the venture although it did say it would be based on a shared industry database of "hashes" - or digital fingerprints - that identify violent content.

Image: Google, which owns influential YouTube, is getting involved

The statement added: "Each company will independently determine what image and video hashes to contribute to the shared database.

"No personally identifiable information will be shared, and matching content will not be automatically removed.

"Each company will continue to apply its own policies and definitions of terrorist content when deciding whether to remove content when a match to a shared hash is found."

The database is expected to be up and running by early next year and more companies could potentially join the partnership.

Social media platforms have come under increasing pressure in recent years from governments across the globe that wanted them to find ways of blocking posts promoting violence or hate.

Islamic State and other groups have used social media websites as a tool for recruiting and radicalisation.

August: Social networks 'failing' to tackle terrorists

The companies themselves have argued they want to be open to free speech - but without being used to promote violence or hate.

YouTube and Facebook are already using hashes to automatically remove extremist content, but many other tech companies relied until now mainly on users flagging up suspicious content.

Twitter said it suspended around 235,000 accounts between February and August this year and also expanded its teams reviewing reports of extremist content.

But critics have said the firms should be doing more. At least one victim of the 2015 Paris attacks has filed a lawsuit in France seeking to hold Facebook, Google and Twitter liable for the violence that led to the huge loss of life.