A valuable and unique part of library collections, certain types of optical discs are becoming obsolete and face a variety of risks ranging from physical damage to loss or theft. In order to protect the content of optical data discs in Czech libraries, a collaborative software tool was developed. The CD-Ark software is designed to store data from the discs, creating data packages that include an ISO disc image alongside with a checksums, as well as technical and bibliographic metadata; the whole package is uploaded onto a joint server, ensuring bit-level preservation.