Platform Sorting Drives Ideological Fragmentation in the Social Media Ecosystem
Edoardo Di Martino, Alessandro Galeazzi, Matteo Cinelli, Michele Starnini, Walter Quattrociocchi
arxiv.org/abs/2606.10575 [ππ.ππΈ ππ.π²π πππ’ππππ.πππ-ππ]
ALT Ideological asymmetries in online political communication are often studied as localized phenomena emerging within communities. Here, we show that fragmentation instead operates at the level of entire platforms, consistent with a process of platform sorting in which users increasingly align with ideologically congruent environments. We analyze political information dynamics across Bluesky, Facebook, Reddit, Truth Social, Twitter/X, and YouTube during the 2020 and 2024 US presidential elections, combining measures of content sharing, engagement allocation, and user-level ideological orientation. Across platforms, ideological fragmentation emerges consistently and persists over time. Platforms exhibit distinct ideological profiles that persist across the two election cycles, ranging from strongly left-leaning to strongly right-leaning environments. Longitudinal analyses further reveal limited ideological variability among persistent user cohorts, indicating that apparent changes within s