Search engines for peptide identification struggle to deal with modified amino acids due to the combinatorial explosion of candidate peptides. Every modification essentially doubles the search space, and this results in a combinatorial explosion. Currently Unimod contains over 1000 possible modifications; taking all modifications into account would result in an unusable large search space. Expansion of the search space usually results in more ambiguity in the identification and unacceptable long computation times. This tool enables researchers to scan for oxPTMs in their spectra. The prediction can be used to, for example, reduce the search space and score peptide to spectrum matches.