The TPP developers have participated in the PSI since 2006, and were instrumental in the development of mzML and many other PSI standards. mzML is the recommended format for TPP input spectra, although the legacy mzXML 64 is still supported. While the TPP still maintains its own internal pepXML and protXML formats for operational efficiency, import and export to mzIdentML are fully supported via tpp2mzid and idconvert as described above. Comet and the TPP were one of the first tools to implement the PSI Extended FASTA Format (PEFF) standard , demonstrating its use in detecting known mass modifications and single amino acid variants . The ProteoMapper tool supports PEFF files as input as well. The TPP is also one of the first tools to support the Universal Spectrum Identifier (USI) standard with its ProForma 2.0 67 peptidoform notation. The TPP spectrum viewer accepts USIs for viewing and assists users with determining USIs in their own datasets.