The built-in standardization operations currently include, among others, standard RDKit sanitization, fragment removal, and neutralization. The built-in filters include checks for overlapping atoms and molecules with SGroup data indicating that they are polymers. The full list is available in the GitHub repository. The current set is fairly minimal and we anticipate that more standardization and filtering options will be added as lwreg evolves. Adding new options is quite straighforward. It just requires implementing a new Python class that inherits from a class provided by lwreg and providing a name, some documentation, and a single function that returns a molecule (the input molecule for filters or the modified molecule for standardization operation) when successful or None on failure. It is possible to apply multiple standardization operations and filters in a user-specified order. The default standardization and filters for an lwreg database are stored as configuration information in the database itself and the particular operations, which were applied for each molecule, are stored with that molecule's information in the database.