 Preserving data is an important aspect of research data management. It aims to keep data and relevant documentation safe, available and usable in the long term. There are several good reasons why research data should be preserved. First, it is necessary to make sure that your research can be verified and reproduced. Besides, preserving data guarantees that it can be reused in the future to perform additional research or for other purposes. This is why data preservation is often an institutional mandate and might be required by other research stakeholders, such as funding agencies. It is important to check whether you are required to preserve your research data and for how long. Preserving data requires a little bit more effort than simply not deleting it. It involves a series of actions to prevent data from becoming unavailable and unusable over time. After all, what's the point of keeping data if it cannot be used? There are several risks that in practice can make data unusable. For example, data can become gradually corrupted because of degradation or failure of storage media. Hardware, software and certain file formats can get outdated, making files effectively unusable. In research institutions, colleagues come and go and sometimes people simply do not know that the data exists or perhaps we don't know where it is kept or what exactly is kept. Sometimes, we are not able to make sense of the files that are left. Keeping data without appropriate metadata and documentation makes the data of little value. Preserving data involves a few steps. First, we need to carefully think what should actually be preserved. Second, we need to select an appropriate medium or a suitable location where data will be kept in a safe way. Finally, we will need to prepare the data for preservation together with its corresponding documentation. Once data has been archived, it is important to do regular checks to spot possible issues such as file degradation before it is too late. Let's have a look at these steps. Preserving takes some time and effort, and making a selection is an essential step of the process. What should be preserved depends highly on the context, but there are some criteria to help. Start from mandatory requirements. Are you legally or ethically required to preserve data, or some parts of it, for a certain period of time? Is it mandated by your institution or research funder? Another aspect to consider is, for which purposes are you preserving data? Is it for research verification? Or do you intend to reuse it in the future? Would you like to allow others to use it as well? What would be needed or useful in such cases? Additionally, it is important to think about the uniqueness and value of data. Some data are simply unique and cannot be recreated. Or perhaps recreating them would be extremely expensive. Other data have great scientific, historical, or cultural significance, or are very likely to be reused. These are all good reasons to select data for preservation. Finally, in some occasions, costs of preservation are very low, and the benefits of preserving simply outweigh the costs. The other side of the picture is that there can be valid reasons for not preserving some data after finishing your research. Think about redundant copies or intermediate files, or superseded versions. And in the long term, after the retention period has expired. And where should data be preserved? We should choose an appropriate location that guarantees that data will be secure and remain accessible to those who need to access it after the end of the project and for the necessary preservation period. Typically, we can choose from two different options. We can deposit data in external data repositories or archives. This is the preferred choice when data can be publicly shared, and when one of the main goals is to enable data reused by others. Keep in mind that this does not mean that data should be shared in a fully open way. Many repositories will allow you to deposit data under different degrees of openness, and to impose certain restrictions on the use of data, or even embargo periods. In other situations, data should be kept in-house, making use of the institutional infrastructure available to you. This is the case when there are reasons why depositing data externally may not be the best approach. And yet, data should be preserved at least for research verification purposes. Regardless the location you choose to preserve your data, you should make sure that certain conditions are met in order to keep data secure, understandable and usable over time. For example, it is a good idea to convert your files to a more sustainable and open format. Keep files organized and give them meaningful and future proof names. Besides, make sure to include enough metadata and documentation to allow others, or your future self, to make sense of the data. Finally, think about who should access the data, which users should be allowed, and under which conditions. Then, take the technical measures to implement these decisions. Preserving data is an essential aspect of research data management, and ensures that data can be accessed in the future, for further reuse, or for research verification. But, preserving data implies more than simply not deleting it, and it requires some preparation efforts. The earlier you start managing your data, keeping it organized, and documented, the easier it will be to get data ready for preservation. For more information, have a look at our web pages.