On March 12th,2004 there was a discussion about client/server communication on the SVG irc channel. Jim Ley suggested to me to have a look at  JSON because it is a simple encoding scheme. Me being a fan of XML-RPC of course favoured XML but I had a look at it anyways. I implemented my own json module in JavaScript? and was thinking that it would be interesting to use it for RPC Before finishing up that thought Robin Berjon said "someone should define JSON-RPC" In the evening of March 12th, I started doing exactly that.

Since 2004, there have been additional specifications and changes proposed by the members of the mailing list.

The current version of the specification can be found at  JSON-RPC 2.0, which is hosted by Matt Morley (MPCM).

For more details about the differences in the versions, see this document by Roland Koebler:  Differences between 1.0 and 2.0