Some Googling turned up this protocol descriptor: https://uploads-ssl.webflow.com/5ba40927ac854d8c97bc92d7/5bf4197268f8b277dbb7c12d_opra_output_binary_dr_spec.

Some Googling turned up this protocol descriptor: https://uploads-ssl.webflow.com/5ba40927ac854d8c97bc92d7/5bf4197268f8b277dbb7c12d_opra_output_binary_dr_spec.pdf https://uploads-ssl.webflow.com/5ba40927ac854d8c97bc92d7/5bf... If you're optimizing for latency JSON is pretty terrible, but most people who use it are optimizing for interoperability and ease of development. It works just fine for that, and you can recover decent bandwidth just by compressing it.