Using “transfer-encoding: chunked”, how much data must be sent before browsers start rendering it?

Question

All browsers wait for some content (and sometimes some amount of time, too) before they start rendering a partial http response you have flushed to it across the network - but how much?

Answer 1

I did some research on this today with an url endpoint accepting letting me configure chunk sizes and intervals.

Mac:                       text/html:     image/jpeg:
curl 7.24.0                4096 bytes     
Firefox 17                 1024 bytes     1886 bytes
Chrome 26.0.1410.65        1024 bytes     1885 bytes
Chrome 29.0.1524.0         8    bytes     1885 bytes
Safari 6.0.4 (8536.29.13)  1024 bytes     whole file

Windows XP:
IE8                        256  bytes
Chrome 27.0.1453.94        1024 bytes
Firefox 21                 1024 bytes
Opera 12.15                128  bytes AND 3s have passed

Windows 7
IE9                        256  bytes

Windows 8:
IE10                       4096 bytes

Answer 2

None, if the headers are set correctly.

See Chunked transfer encoding - browser behavior for a thorough explanation.