JabRef can cleanup the entries of a library. To do a cleanup of the entries, go to Quality → Cleanup entries. Then select the actions to be carried out.
under the table
Enable field formatters. Then, under the table, you can select using 2 drop-down menus:
an entry field (upon which the action will be applied).
the type of action to be carried out (such as HTML to LaTeX, which converts HTML code to LaTeX code, as described in the window). See the list of formatting actions.
A click on the "circular arrow" icon enables a set of recommended formatting actions (the set of actions will depend on your database type: BibTeX or biblatex).