JSON has been goto format for data exchange from a while. I think native browser support is biggest reason of its success.
Is there any competing standard? I dont think I miss any features in JSON.
EDN[0] competes in the space, for some value of 'competes'. I think it's better, strictly speaking, but lacking JSON's ubiquity, and relentless simplicity, I expect it will always lack the network effects which are most of what make JSON so powerful.