Change User Agent general.useragent.override in Seamonkey Firefox CentOS 6

Change User Agent general.useragent.override in Seamonkey Firefox

or

Access web.whatsapp.com in Seamonkey

( some material taken from:
Taken from:
https://www.howtogeek.com/113439/how-to-change-your-browsers-user-agent-without-installing-any-extensions/
)


Some sites like web.whatsapp.com do not accept some versions of browsers:



You can easily change this behavior by adding a new 'preference name' in the browser's configuration:

• In URL write:

about:config

• Right click on the names and select 'New->String'
• Write: 

general.useragent.override

• In the string value write a known user agent string like:

Mozilla/5.0 (Windows NT 10.0; WOW64; rv:40.0) Gecko/20100101 Firefox/40.0

If you are using Linux:

Mozilla/5.0 (X11; Linux x86_64; rv:68.0) Gecko/20100101 Firefox/68.0

• And, if it is set, erase the value of:

calendar.useragent.extra

Voilà!:



You can choose from a variety of  user agent strings from:
http://useragentstring.com/pages/useragentstring.php/

For Firefox:
http://useragentstring.com/pages/useragentstring.php?name=Firefox