Many requirements engineering tools have been developed for gathering, documenting, and tracing requirements that can even be further processed for such purposes as analysis and transformation. In this study, we analysed 56 different requirements engineering tools for a comprehensive set of features that are categorised into multiple viewpoints (i.e., project management, specification, collaboration, customisation, interoperability, methodology, and user-support). The analysis results led to many interesting findings. Some of them are as follows: (i) the project planning and execution activities are rarely supported, (ii) multi-user access and versioning are highly supported, (iii) the most popular specification technique is natural languages, while precise specification via modeling languages is rarely supported, (iv) requirements analysis is rarely supported, (v) requirements transformation is considered for generating documents only, (vi) tool customisation via the tool integration and API support is highly popular, while customising the notation set is rarely supported, (vii) exchanging requirements is popular in such standards as ReqIF and Excel/CSV, while no single standard is accepted by all the tools, (viii) agile development is very common, while other methodologies (e.g., MDE and SPLE) are rarely supported, and (ix) user-guides, telephone, e-mail, and videos are the most preferred methods for user-support. The analysis results will be useful for different stakeholders including practitioners, tool vendors, and researchers.