Gmail has been a SPA since launch. There were some pre-launch versions that were not, and it has always had a plain HTML fallback mode.
I believe there may have been some major changes to the way it did the client-side rendering a few years after it launched. The original version was more ad hoc, since it was pretty much the first time anyone (at Google, at least) had built a real SPA. Later they built tools and libraries, and developed a more systematic way of doing things. (I was at Google during that time period, but never worked on Gmail.)
I believe there may have been some major changes to the way it did the client-side rendering a few years after it launched. The original version was more ad hoc, since it was pretty much the first time anyone (at Google, at least) had built a real SPA. Later they built tools and libraries, and developed a more systematic way of doing things. (I was at Google during that time period, but never worked on Gmail.)