Elgg

A powerful open source social networking engine

Collaboration Communication Developer Tools elgg.org

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Founded

2004

Starting Price

Free

About Elgg

Elgg is an award-winning open-source social networking engine that provides the core components needed to build socially aware web applications. It offers a flexible, plugin-driven architecture with a well-documented API, enabling developers to create anything from university campus networks to enterprise collaboration platforms. With over 1,000 community plugins available, Elgg can be extended and customized to meet virtually any social networking requirement.

Pros & Cons

Pros

Completely free and open source under the GPL, with no vendor lock-in or licensing costs
Highly extensible plugin and theme architecture with over 1,000 community-contributed extensions
Strong built-in security features including CSRF protection, XSS filtering, and modern password hashing
Full data ownership — self-hosted deployments keep all user data under the organization's control
Active development community and long track record since 2004, indicating project maturity and stability
Flexible enough to power diverse use cases from academic networks to enterprise intranets

Cons

Requires PHP/MySQL server knowledge to install and maintain, making it inaccessible to non-technical users
No hosted SaaS version; organizations must arrange their own hosting and server management
Admin and moderation tooling is less polished compared to commercial social networking platforms
Smaller plugin ecosystem and community compared to platforms like WordPress
Frontend design feels dated out of the box and typically requires significant theming effort for a modern look

Key Features

Well-Documented Core API

A comprehensive and stable API that enables developers to start building social applications quickly and integrate custom functionality with ease.

Plugin Architecture

A flexible system of hooks and events allows developers to extend or override almost any core behavior without modifying the core codebase. Over 1,000 community plugins are available.

Access Control System

Granular content permission controls let users and administrators define exactly who can view or interact with any piece of content on the platform.

Built-In Security

Includes anti-CSRF validation, XSS filters, HMAC signatures, and advanced password hashing using modern cryptographic methods to protect user data.

Flexible Entity System

A generic entity model allows developers to rapidly prototype and deploy new content types such as posts, files, events, or any custom object.

User Profiles and Groups

Native support for user profiles and group communities, enabling community formation and collaborative spaces within the platform.

Notifications Service

Built-in notification system supporting both on-site alerts and email notifications, keeping users engaged with activity on the network.

Internationalization Support

Full i18n support compatible with services like Transifex, making it straightforward to deploy Elgg in multiple languages for global communities.

Web Services & RPC

RPC web services layer and a client-side JavaScript API via RequireJS enable third-party integrations and rich, dynamic front-end experiences.

Composer Package Management

Uses the Composer package manager for simplified installation, dependency management, and platform maintenance, following modern PHP best practices.

Pricing

Open Source (Self-Hosted)

Free

Full source code access on GitHub
Core social networking engine
Plugin and theme system
Community forum support
Access to 1,000+ community plugins
Comprehensive developer documentation

Professional Services

Custom

Certified service providers available
Custom development and theming
Managed hosting options
Enterprise support contracts
Elgg Foundation supporter scheme

Best For

University and Academic Networks

Higher education institutions use Elgg to build campus-wide social networks connecting students, faculty, and staff with profiles, groups, and activity feeds.

Enterprise Intranet and Collaboration

Organizations deploy Elgg as an internal collaboration platform where employees can share knowledge, form working groups, and communicate across departments.

Nonprofit and Community Platforms

Nonprofits and NGOs leverage Elgg to build member communities and advocacy networks where data privacy and ownership are critical priorities.

Custom Social Network Development

Developers and agencies use Elgg as a foundation to build bespoke social networking applications for clients, taking advantage of its flexible API and plugin system.