Is there a reason that the JSON response content-type does not indicate charset=utf-8?

[benwilber]

Looking at this code here:

https://github.com/tokio-rs/axum/blob/main/axum/src/json.rs#L194

It's just doing application/json

But the JSON spec requires UTF-8 encoding except for "closed systems".

JSON text exchanged between systems that are not part of a closed
ecosystem MUST be encoded using UTF-8 [RFC3629].

It seems to me that the most common case (not a closed system) will always require UTF-8 encoding for JSON responses. I run into this frequently when using things like emojis in a JSON response and they show up as escape codes instead of emojis because Json(..) does not indicate the charset in the content-type.

[anarchodin]

From RFC 8259, section 11:

Note: No "charset" parameter is defined for this registration.
Adding one really has no effect on compliant recipients.

[davidpdrsn]

Ah I didn’t know this. But that possibly explains why the mime crate (which axum uses) doesn’t have a charset for application/json.