Although originally conceived and developed as part of mzSpecLib, a standardized format for encoding fragment peak annotations has been split into a separately proposed standard (see details at ). This was done in order to keep the mzSpecLib specification smaller, because the annotations for other types of molecules, such a lipids and glycans, would be quite different but envisioned as an add-on to mzSpecLib, and finally because a standardized annotation format may be useful in other contexts, such as in spectrum viewers and figures containing annotated spectra. The formatting is based substantially on the NIST MSP peak annotation formatting, which has evolved over the years but was never documented. Several components differ from NIST MSP conventions by general consensus, with participation by NIST as well. This peak annotation format is about to enter the DocProc.