A more detailed breakdown of the PFAS sections according to the updated OECD definition 3 is shown in Figure . Figure reveals that 6.5 million PFAS fit this new definition (excluding salts and mixtures), of which 5.7 million contain an isolated CF 3 group, ~670,000 an isolated CF 2 group and ~230,000 a PFAS moiety larger than CF 2 /CF 3 -in other words, ~230,000 PFAS also satisfy the 2011 Buck et al. PFAS definition of substances containing at least CF 2 -CF 2 . As shown in Figure , this can be broken down further to determine e.g., how many molecules with an isolated CF 3 also contain larger PFAS parts (~27,000) and whether the parts are linear, branched, cyclic, and so on. As shown in the bottom of Figure , the breakdown will eventually reveal the formulas of the PFAS part (here C 2 F 4 -note the leading zeros are added to maintain a logical sorting order), should a given chain length be of interest. The total number of nodes in the tree is very high (currently 9890 nodes, June 2023). The nodes below the major sections are created dynamically depending on the data to maintain performance and functionality. As a result, formulas and other nodes appear once certain conditions are met -more details are given in the documentation . Suspect lists and/or databases can be created for workflows by clicking on the nodes of interest (i.e., the blue numbers), which will open a search window to either browse or download the entries. The download file contains several fields of interest; details on how to perform searches and downloads are given in the documentation . Figure shows the breakdown of PFAS including salts and mixtures, with ~1 million additional entries due to salts and mixtures. The difference in numbers on the "OECD PFAS definition" total (6.51 million) versus the "Neutral" category (6.44 million, 3 rd row of Figure ) is due to differences in the processing as well as ambiguities in the wording of the PFAS definition. Currently, this difference is being maintained to enable an easier comparison of these "edge cases" (cyclic PFAS and PFAS-ether cases) and thus to stimulate discussion with experts within the PFAS community to help develop/refine PFAS definitions in a way that is both easy to understand and implement consistently with automated cheminformatics approaches (discussed further below). Figure also reveals additional ways of browsing the PFAS content in a complementary manner to Figure , including by functional groups (with the PFAS part connected to C, N, O, P, S or other elements), by connectivity (with only one connection, i.e., where the PFAS is a terminal part of the molecule, or with two or more connections to the PFAS part) and by formulas, so that it is possible to search by the length of the PFAS part if a particular chain length is of interest. Again, leading zeros are present in formulas to enable a logical sort order of the formulas since the classification browser nodes appear alphabetically. The section shown in Figure can be broken down by each of the respective categories, such that it is possible to exclude salts and mixtures, or only search for PFAS formulas connected to S, and so on. The dynamic "PFAS breakdowns by chemistry" section (Figure ) contains 24,600 nodes, over double the number of nodes in the "OECD PFAS definition" section (Figure ). Further details and examples are again given in the documentation and explained in the webinar .