There are also challenges associated with the ever-increasing size of spectral libraries. First, this makes it more difficult to process the data, and better compute infrastructure and optimized algorithms are necessary to process large spectral libraries . Cloud-based solutions, such as the GNPS analysis platform, have the potential to be extremely scalable while hiding this complexity from the user. For example, GNPS allows users to query their data against 1.2 billion open MS/MS spectra using the Mass Spectrometry Search Tool (MASST) to discover public datasets that contain similar MS/MS spectra (M. . Developing and maintaining such platforms requires suitable, continued investments and a team willing to maintain the resources for the benefit of the community. The same is also true for MetaboLights , Metabolomics Workbench , HMDB , MetaboAnalyst , MZmine , MS-DIAL , and other popular untargeted metabolomics resources. In response, to overcome some of these challenges, subscription models or commercial libraries such as NIST, mzCloud, or METLIN Gen2 continue to be needed. Second, interoperability of various tools and resources is important. There currently does not exist an official data standard for spectral libraries yet. Frequently used spectral library file formats include the mzML , mzXML , Mascot Generic Format (MGF), and the NIST MSP formats. Unfortunately, some of these formats are only loosely defined, change over time, often without explicit versioning, and spectrum metadata can be encoded in various non-standardized ways, limiting the usability and portability of such spectral library files. The Proteomics Standards Initiative of the Human Proteome Organization (HUPO-PSI) , which has previously developed fundamental mass spectrometry data standards such as the mzML peak file format , is currently working on a specification for spectral libraries (). Although the HUPO-PSI primarily develops data standards for proteomics, many of their efforts are relevant for any application of biological mass spectrometry. The HUPO-PSI working groups are open to any community contributions, and interested parties are encouraged to engage in the development of this nascent spectral library format to ensure its full compatibility with applications in metabolomics.