Radical Filter Bubbles: Social Media Personalisation Algorithms and Extremist Content

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This paper assesses whether social media platforms’ personalisation algorithms promote extremist material, finding evidence that only one platform studied – YouTube – prioritises extremist material by the recommender system.

Global Research Network on Terrorism and Technology Paper

Key Findings

  • Investigations were conducted on three social media platforms – YouTube, Reddit and Gab – to establish whether the sites’ recommender systems promote extremist material.
  • The recommender system of one social media platform – YouTube – prioritises extreme right-wing material after interaction with similar content, supporting the findings of a previous study.
  • The authors do not find evidence of this effect on either Reddit or Gab. This is significant as Gab has been identified by many as a safe haven for extreme right-wing movements. This finding suggests that it is the users, rather than the site architecture, which drives extremist content on Gab.


  • Social media platforms should consider removing problematic content that does not break their terms of service from the recommender system, effectively quarantining it.
  • Platforms should prioritise recommending high-quality sources (such as news outlets with established editorial departments) when users are interacting with problematic or controversial content that does not clearly violate their policies.
  • Social media platforms should provide greater transparency in social media recommendations, including a clearly identifiable ‘why am I being recommended this?’ option on platforms.
  • Further research should be conducted, particularly on closed platforms or sites that currently do not permit such research in their terms of service. This can only be done in close collaboration with social media platforms.

Alastair Reed is an Associate Professor at Swansea University; he is also an Associate Professor at TU Delft in the Netherlands.

Joe Whittaker is a doctoral student at Swansea University and Leiden University. He is also a research fellow at the International Centre for Counter-Terrorism.

Fabio Votta is a graduate student in Empirical Political and Social Research at the University of Stuttgart.

Seán Looney is a doctoral student at Swansea University and Université Grenoble Alpes.

Correction: On 26 July 2019 at 14:11 GMT, Figure 1 was amended.


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