Creating a dynamic, user-friendly, browsable, and intuitive resource to explore >21 million fluorinated compounds in PubChem has been an incredibly challenging exercise in informatics and design, with several draft approaches attempted and revised before settling on the current version presented here. The functionality remains under development; automation of the regulatory and suspect list sections will be improved as the required functionality is developed. The handling of PFAS ethers (CF 2 -O connections) and cyclic PFAS structures has been particularly challenging, along with the implementation of automated queries for the PFOA exemptions and the related compounds for the LC-PFCAs (as described above). While salts and mixtures have been added to the OECD PFAS section (resulting in an extra million CIDs included in the PubChem PFAS Tree), these are still missing in the "Organofluorine compounds" and "Other diverse fluorinated compounds" sections. With rising awareness of fluorinated counterions increasing in concentrations in wastewater and potentially becoming problematic for treatment and thus drinking water production , adding this is a shorter term future development, which may add a few million more CIDs to the PubChem PFAS Tree. Polymers and UVCBs will be added to the PubChem PFAS Tree once PubChem functionality is available to do so -and will likewise increase numbers further.