Metadata can be created manually or using specific tools. Tools, also for subject-specific metadata, are available online and often free to use. However, ask colleagues or data managers at your institution about established routines or licences for proprietary software commonly used in your research area. The following tools for creating metadata are only a selection (also Table 2). Maintaining tools and software packages is a lot of work, so some tools may be discontinued after a while. The important step is to add metadata to your data. Which tools you use is secondary.

A simple way to create metadata is to use a table with the elements of your chosen metadata standard as columns. You can use any spreadsheet software to set this up. For example, GBIF provides templates for occurrence data, checklist data, sampling event data and resource metadata following the metadata standard Darwin Core, an extension of Dublin Core that facilitates the sharing of information about biological diversity. GFBio provides more specific templates which also prepare sample depositions in German data centers for different sample types and taxa (organisms, tissue, molecular data, etc.). All of these templates are spreadsheets with details on minimum metadata requirements.

RightField is an open-source tool which sets up or helps you fill in simple spreadsheet tables depending on the metadata standard you choose. Ontologies can either be imported from local file systems, the web, or from the BioPortal ontology repository. RightField translates these ontologies into a spreadsheet table, and you only have to choose from the predefined terms to create your standardised metadata. You can build your own templates, too, but we highly recommend using an existing, widespread metadata standard to make your metadata findable and interoperable.

Tools with simple graphical user interfaces are not available for all metadata standards. Therefore, if you want or need to work directly with an existing XML metadata standard, you should either use the free editor Notepad++ or the paid software oXygen, if licences are available at your institution. Both editors offer better usage and display options to make content and element labels visible separately.

To create metadata in the XML metadata standard EML (Ecological Metadata Language), you can use the online tool ezEML. ezEML is free of charge and only requires a registration. It can be used as a “wizard” to guide you step-by-step through the creation of your EML document. However, ezEML also offers a range of other workflows, such as data table upload, and checking your EML document for correctness and completeness. 

The open source online tool CEDAR Workbench allows online templates based on metadata standards to be created via a graphical user interface, filled in and also shared with other users. At the same time, templates created by other users can also be used for one's own research. All you need to do is register free of charge. If you are working with biodiversity survey or monitoring data, you can use the ADVANCE template in CEDAR based on a controlled vocabulary integrating terrestrial, freshwater, and marine monitoring metadata to facilitate data interoperability and analyses across realms.

The ISA framework (Investigation, Study, Assay) is suitable for experiments in the life sciences and environmental research. It is open source and consists of several programmes that can help in the management of experiments from planning and conduction to the final description. You can start with the ISA Creator, which is used to create files in the ISA-TAB format. This format is explicitly required, for example, by the Scientific Data Journal of the Nature publishing house.

Which programmes are suitable for your metadata depends very much on the type of research data and your wishes for use (also see Table 2 & Table 3). It is therefore worthwhile to talk to other researchers in advance to find the best way to create metadata for yourself. Familiarising yourself with the metadata standard relevant to you and searching for programmes that use this standard can have an advantage in terms of automatic processing of the data and later publication. At the very least, the use of a simple, subject-independent metadata standard such as Dublin Core should be considered. Of course, you should try to use the most suitable metadata standard, especially with respect to the recommendations of the chosen repository; however, there is no such thing as a perfect choice. Overall, huge effort is invested in making metadata standards interoperable in the future.