Where the words added with the User Dictionary are stored?

Depending on the type of the product used the initial storage for words will be different.

SpellCheckAsYouType (SCAYT):

By default, all words added using SCAYT User Dictionary functionality will go to the browser local storage. Thus, all the words will be stored on the end user’s side and will be available from a particular browser. The words added using WSC User Dictionary functionality will be saved in browser cookies, as well on the end user’s side.

WebSpellChecker Dialog (WSC)

In order to have access to a personal dictionary and be able to use it from different browsers and machines (or devices) while working with the system, the end user has to “Create” a dictionary from “Dictionary” tab of SCAYT or “Options” section of Spell Check Dialog. This dictionary will be stored on the server. In case with the Hosted/Cloud version of WebSpellChecker services, such a dictionary will be stored on the WebSpellChecker servers. For the Licensed/Server version – on the client’s server where the WebSpellChecker application is installed and running (<installation_folder>\WebSpellChecker\AppServer\userdict).

Thus, as soon as the user decides to create a personal dictionary on the server, all the words from cookies (WSC) or local storage (SCAYT) will be moved to the dictionary on the server.