Online Social Networks are digitally mediated networks of social relationships formed, maintained, displayed or activated through internet-based communication systems and platforms. They can include relationships between friends, relatives, acquaintances, community members, interest groups, creators, audiences and other participants whose interactions occur partly or primarily online. The term describes a social structure as well as the technological environments that facilitate it, so it should not be reduced to a particular type of website or application.
An Online Social Network can be represented as users connected by relationships such as following, friendship, messaging, commenting, sharing, membership or interaction. Some connections are reciprocal, while others are directional, such as following a public account without receiving an equivalent connection. The network may be explicit when a platform displays a list of connections, or implicit when relationships are inferred from repeated interaction.
Online Social Networks differ from offline networks because digital systems can store, search, recommend, rank and algorithmically organise interactions at scales that are difficult to reproduce in face-to-face settings. Nevertheless, online relationships frequently overlap with offline relationships, making the boundary between online and offline social life increasingly difficult to treat as absolute.
Online Social Networks have several structural properties that distinguish them from many traditional forms of social interaction. Digital platforms can support extremely large networks, persistent records of communication and rapid transmission of information across geographical boundaries. Network visibility can also make social connections observable to participants, although privacy settings and platform design determine how much information is exposed. Users can participate in multiple overlapping networks simultaneously, including family networks, friendship networks, professional communities, interest-based groups and public audiences.
Network structures may contain clusters formed around shared interests, institutions, identities or communities, with some users occupying bridging positions between clusters. Algorithms can influence which connections become salient by ranking content, recommending accounts and determining what appears in feeds. This means that the technically available network and the socially experienced network are not always identical. A user may technically be connected to hundreds of people but regularly encounter only a small subset through algorithmic filtering. Online Social Networks therefore involve both relational structures created by users and computational systems that mediate the visibility, ordering and circulation of social activity.
The development of Online Social Networks followed earlier forms of computer-mediated communication, including electronic mailing lists, discussion forums, bulletin board systems, chat services and online communities. Later platforms introduced persistent user profiles, visible connection lists, personal publishing and mechanisms for discovering other users, creating network structures that became central to everyday internet use.
The historical development of these systems involved a gradual shift from relatively specialised online communities towards platforms used for general social communication, media distribution, professional interaction, commerce and public communication. Mobile internet access further integrated online networking into routine daily activity by allowing users to maintain connections continuously rather than only from fixed computers. Platform development has also introduced increasingly sophisticated recommendation systems, automated moderation, advertising systems and data analytics.
The history of Online Social Networks is therefore not simply a sequence of websites but a transformation in how digital communication, identity presentation, social discovery and information distribution are organised. Earlier systems often emphasised direct communication and community participation, whereas contemporary platforms can combine interpersonal communication with broadcasting, algorithmic recommendation, commercial activity and large-scale public audiences.
Online Social Networks serve numerous social functions. They enable people to maintain relationships across distance, coordinate activities, share experiences, discover communities, exchange information and participate in collective activities. They can be especially important for geographically dispersed families, migrants, people with specialised interests and communities whose members are distributed across different locations. Online groups can create opportunities for mutual support and knowledge exchange that might be difficult to establish locally.
At the same time, online communication changes the conditions under which interaction occurs. Messages can be asynchronous, interactions can be publicly visible, audiences can be larger than intended and content can remain accessible after the original context has disappeared. Context collapse can occur when content intended for one social group becomes visible to several different audiences with conflicting expectations. The persistence and replicability of digital content can also alter how relationships are managed. A statement made in one context may later be encountered by employers, relatives or unrelated audiences. Online Social Networks therefore provide significant opportunities for connection while introducing distinctive challenges involving audience management, context, persistence and visibility.
The informational role of Online Social Networks is closely connected to their network structure and algorithmic systems. Information can spread through direct sharing, reposting, recommendation, commenting and other forms of interaction, with highly connected or highly active users potentially acting as transmission points between different groups. Information diffusion does not necessarily follow a simple linear process because users encounter content through multiple overlapping pathways.
Homophily can produce clusters in which people with similar interests or beliefs interact frequently, potentially reinforcing shared interpretations. At the same time, bridging connections can expose users to information from different communities. Algorithms may amplify particular forms of content according to platform-specific objectives and ranking systems, meaning that visibility is not determined solely by interpersonal relationships. Misinformation, rumours and accurate information can all travel through network structures, so the existence of an extensive network does not guarantee information quality. Researchers therefore distinguish between network connectivity and information reliability. Understanding Online Social Networks requires examining both who is connected to whom and how technical systems affect what those connected users actually see, share and discuss.
Online Social Networks also transform identity presentation and relationship management. Users can select profile information, images, affiliations and forms of self-description that communicate particular aspects of identity, although the extent of control varies between platforms and social contexts. Social interaction can involve impression management because participants may anticipate how different audiences will interpret visible activity. Some relationships remain relatively private through direct messaging, while others become partially public through comments, reactions or shared content.
The distinction between audience and network is therefore important because a user's network can contain people with very different expectations and relationships to that user. Digital identity can also persist across time, meaning that historical activity may remain available after a person's circumstances have changed. This can create continuity but also difficulties when old content conflicts with current identity or context. Online Social Networks additionally permit forms of social participation that combine observation and interaction. People may consume content without actively responding, monitor other users without direct communication or participate in communities through low-intensity activities. Such behaviours demonstrate that social connectedness online cannot be measured only by visible messages or explicit friendships.
Privacy and governance are major areas of study within Online Social Networks because digital relationships generate extensive information about social behaviour. Platforms can collect data about connections, interactions, location signals, device use, content engagement and patterns of communication, depending on the platform and applicable rules. Privacy risks can arise from public disclosure, unwanted contact, data breaches, secondary use of information, account compromise or the ability to infer sensitive characteristics from apparently ordinary network data.
Moderation systems are also important because large networks require mechanisms for dealing with harassment, abuse, fraud, spam and other harmful behaviour. Automated moderation can operate at enormous scale but may make errors or struggle with context, while human moderation can be resource-intensive. Platform governance determines rules for participation, visibility, account enforcement and content distribution, meaning that Online Social Networks are not purely neutral communication channels. Researchers and policymakers therefore examine questions of privacy, platform accountability, user safety, competition, data governance and freedom of expression alongside the social benefits of digital connectivity.
Online Social Networks are studied using surveys, interviews, ethnography, experiments, network analysis and computational analysis of digital trace data. Researchers may examine friendship structures, follower networks, interaction patterns, information diffusion, community formation and changes in network membership over time. Ethical research is particularly important because online data may concern people who did not expect their activity to be studied, and apparently public information can still involve contextual privacy expectations.
Network data can also create reidentification risks because combinations of relationships may uniquely identify individuals or groups. A common misconception is that online networks are separate from real social life, when in practice digital and offline relationships often interact continuously. Another misconception is that the number of visible connections measures social integration, even though connection count does not establish closeness, trust or support. Online Social Networks are best understood as technologically mediated social environments whose structures are produced jointly by users, institutions, cultural practices and computational systems.
