[Help] Can't save json file

I make a level editor for client.

Level design are saved and load with json file.

I can save it on live preview or localhost, but, on exported file (html5) save file are blocked by browser.

Here is the log info:

Mozilla Firefox: Navigation to toplevel data: URI not allowed (Blocked loading of: “data:text/html,<p><a download='level-1.j...”)

Chrome: Not allowed to navigate top frame to data URL: ...

How to allow browser to download json file from script?

Thanks