New study: platform sorting fragments users ideologically across 6 major social networks

Researchers Edoardo Di Martino, Alessandro Galeazzi, Matteo Cinelli, Michele Starnini, and Walter Quattrociocchi analyzed political information dynamics across six major social media platforms—Bluesky, Facebook, Reddit, Truth Social, Twitter/X, and YouTube—during the 2020 and 2024 US presidential elections. They combined measures of content sharing, engagement allocation, and user-level ideological orientation to study how political fragmentation evolves.

The results show that ideological fragmentation is not just a localized phenomenon within communities but operates at the level of entire platforms. Each platform exhibits a distinct ideological profile that persisted consistently across both election cycles, ranging from strongly left-leaning (e.g., Bluesky) to strongly right-leaning (e.g., Truth Social). Longitudinal analyses revealed limited ideological variability among persistent user cohorts, indicating that apparent changes within single platforms reflect ecosystem-level sorting rather than convergence toward neutrality.

The study concludes that platform sorting is not a transient reaction to political events or moderation interventions, but a persistent structural feature of the social media ecosystem. This challenges the common narrative that fragmentation happens primarily through algorithmic echo chambers within a single platform; instead, users are increasingly selecting platforms that match their pre-existing ideologies, leading to more polarized and divided online public spheres.