When you use the Old Handwriting extension it will use memory in the browser. The more active tabs you have open with the browser extension, the more memory it will use. So if the browser appears to be running slowly or if you see the error message "Out of session memory", then closing the other browser tabs may help. To completely release all memory for all tabs and all browser extensions, quit and restart the web browser.

Just having the Old Handwriting extension installed in your browser does not use up any significant memory or other resources.