I thought we’re talking about convenient copy pasta action here, if you’re serious about the data you would have it in a .json file anyways.
if you’re just copy pasting, you’re probably using some REPL, it’s not like you can copy 1GB of JSON anyways (if you’re, you’re doing it wrong), the performance change is unnoticeable considering your fingers on keyboard and mouse time.
also, compile time or not, how can you validate a JSON string without parsing it?