There are a handful of free tools available to conduct network analysis. No matter which field you belong to, network analysis and visualizations can greatly enhance your understanding of key players within a network or a community.
I would categorize these tools by the level of difficulty in terms of learning a programming language (such as R) or simply navigating your way through a relatively easier program (needing no programming skills). Prominent network analysis tools include Gephi, NodeXL, Ucinet, Pajek, and iGraph package in R.
The major network analysis tools that help us understand the network structure are:
Amongst all, I would list Gephi and NodeXL at the top simply because of their capabilities, ease of use, and free availability (basic version of NodeXL is free). In my opinion, both Gephi (open source) and NodeXL are good tools. In terms of graph visualizations Gephi can create more beautiful network charts. When network size becomes an important consideration Gephi enables more clear and aesthetically pleasing visualizations. However, NodeXL provides more detailed and varied numbers from the network analysis.
Gephi: This is an open-source graph visualization software (for both Windows and Mac) and can be installed on a desktop. Gephi is one of the most popular network visualization software, and does not require any programming knowledge. Gephi visualizations are also the most appealing and easier to comprehend especially when the network size is large (up to 100,000 nodes). Gephi can easily calculate common metrics such as degree, centrality, eigenvector centrality, network diameter etc. It must be mentioned that Gephi is stronger on the visualization capabilities and NodeXL does a better job at computing network metrics.
NodeXL: The great thing about NodeXL is that its learning curve is not as steep since it is an Excel add-on. Anyone who knows how to use Excel can easily learn NodeXL. However, the network analysis and visualization tool offers less in terms of the quality of visualizations (in comparison with Gephi). Another problem is that NodeXL is currently not compatible with Mac systems. You must have a Windows based computer to run NodeXL. NodeXL does offer the option to collect data directly through major APIs of social networks (e.g. Twitter API).
Ucinet: This is the third major network analysis tool that is more popular in academic circles. Ucinet also offers a wide range of network analytics capabilities, however, it is limited in terms of quality of visualizations. Ucinet is only Windows based so Mac users have to rely on a compatible tool such as Gephi.
Pajek: Pajek also offer various functionalities for network analysis (especially large networks) and is free for non-commercial use. Pajek features are are similar to Ucinet and is widely used for analysis and visualization. The word Pajek is Slovene word for Spider. The use of the program is not as user-friendly as Gephi and NodeXL, but it offers a great deal of value for those interested in visualizing large networks.
NetMiner: As per their website, “NetMiner is an premium software tool for Exploratory Analysis and Visualization of Network Data”. NetMiner has an interesting interface that allows you to explore network data visually and interactively. NetMiner is mainly used for research and teaching purposes.
Social Networks Visualizer: Social Network Visualizer (SocNetV) is a cross-platform, user-friendly free software application for social network analysis and visualization. The great thing about SocNetV is that it is available for Windows, MacOS and Linux, and the program helps easily calculate various network metrics. It has an easy to use interface, offering intuitive visualization layouts on undirected/directed graphs.