The Collective Spectral Library (CSL) is a database containing a collection of reference spectra generated using high-resolution tandem mass spectrometry (HRMS²). The CSL is built collaboratively and currently includes reference spectra provided by: Federal Institute of Hydrology (Bundesanstalt für Gewässerkunde, BfG), Koblenz, Germany Bavarian Environment Agency (Bayerisches Landesamt für Umwelt, LfU Bayern), Augsburg, Germany German Environment Agency (Umweltbundesamt, UBA), Berlin, Germany The CSL enables retrospective screening of environmental samples as part of Non-Target Screening (NTS) efforts. It is integrated into the open analysis workflow ntsworkflow [1], which supports matching of experimental MS² data with verified reference spectra. It is also connected to NTSPortal [2], a platform for processing, archiving and visualizing NTS data to support the identification and assessment of trace contaminants in surface waters. We continuously expand the CSL to improve its utility, for instance in the retrospective analysis of historical data in NTSPortal. For more information, feedback, or to contribute spectral reference data feel free to contact us at ntsportal@bafg.de. References [1] Jewell, K. S., et al. (2020). Rapid Commun. Mass Spectrom., 34, e8541. https://doi.org/10.1002/rcm.8541[2] Jewell, K. S., et al. (2025). Online-Portal „Non-Target Screening für die Umweltüberwachung der Zukunft“, Umweltbundesamt, Dessau-Roßlau. https://www.umweltbundesamt.de/sites/default/files/medien/11850/publikationen/21_2025_texte.pdf Files CSL_v.dbThe SQLite database containing all reference spectra and related records.This file can be opened with any SQLite-compatible software, such as the open-source DB Browser for SQLite (available at https://sqlitebrowser.org), or accessed programmatically using standard SQLite libraries. thermo-CSLv-.mspAll reference spectra exported in NIST format. This format is readable by software such as mzVault (tested with mzVault Version 2.3 SP1, Thermo Fisher Scientific), and can also be opened with any text editor. A separate file is provided for each chromatographic method for which experimental or modelled retention time data are available. The field PREDICTED_RT indicates the origin of the retention time data for each record. TRUE: retention time is modelled (predicted); FALSE: retention time is experimental. CSL-er-diagram.pngEntity-Relationship diagram of the CSL database structure. CSL-data-dictionary.xlsxData dictionary providing detailed descriptions of all columns in each table. CSL-changelog.mdDetailed record of changes for each version. Versions 25.7 Unified the naming scheme of all tables and columns Restructured tables, columns, and links (see CSL-er-diagram.png) Expanded the data sources table to included additional information General cleanup and corrections 25.6 Added spectra for 41 new compounds Corrected some compound names and standardized adduct notation Fixed incorrectly linked experiments and removed duplicate entries 25.5 Initial version containing 1,721 compounds and 35,523 spectra For more details see, CSL-changelog.md.