Eli Pariser first noticed filter bubbles when he observed that posts from his conservative friends were disappearing from his Facebook news feed. He realized that Facebook was "editing out" certain content, effectively filtering the information he saw based on algorithms tailored to his interests and interactions

. This personal experience led him to identify the phenomenon where online algorithms create a unique, personalized universe of information for each user, limiting exposure to diverse viewpoints and reinforcing existing beliefs

. In summary, Pariser's initial awareness came from noticing the disappearance of certain political content in his social media feed, which revealed how algorithmic filtering shapes the information environment for individuals.