Request Headers. Note Accept. GET /api?method=get_folders HTTP/1.1Accept: application/jsonAccept-Encoding: gzip, deflate, compressAuthorization: Basic ASDFgfdsghstFDASGFDAGRADContent-Type: application/json; charset=utf-8Host: wintermute:8888User-Agent: HTTPie/0.8.0Response Headers. Note Content-Type. HTTP/1.1 200 OKCache-Control: no-cacheConnection: keep-aliveContent-Length: 654Content-Type: text/javascriptContent-Type should obviously be application/json -- we are not returning arbitrary JavaScript (aka JSONP) here. This should be fixed because: 1. sent content-type should match the requested type within reason 2. it's clearly application/json data being returned anyway 3. downstream APIs and tools may not handle text/javascript in the same way This specific example taken from FreeBSD 10.0 client. I'd suggest also you may want to consider including the btsync version in the returned headers. This will be useful in future for feature detection and operations.