At the time when Gmail was being developed, existing email services such as Yahoo!Mail and Hotmail featured extremely slow interfaces that were written in plain HTML, with almost every action by the user requiring the server to reload the entire webpage.
Active users from the Blogger community were offered the chance to participate in the beta-testing on 20 April and later, Gmail members occasionally received "invites" which they could extend to their friends.
In addition, Sprint announced separately that it would make the application available from its Vision and Power Vision homepages, preloaded onto some new Sprint phones.
The application gives Gmail its own custom menu system and the site displays attachments, such as photos and documents in the application.
One round of invitations was sent out on 1 May and another three invitations were given to all active members on 1 June.
When Gmail increased the supply of invitations, the buying and selling market for Gmail invites collapsed.
When the service was finally launched in April 2004, about a dozen people were working on the project.