To set null value in HTTPie, use the := operator, instead of the = operator:
http POST localhost:8000/ foo:=null
This will send the following payload with a null value:
{
"foo": null
}
If you use the = operator, like foo=null, it will send a string instead of a null value:
http POST localhost:8000/ foo=null
{
"foo": "null"
}
Also, foo= will send an empty string:
http POST localhost:8000/ foo=
{
"foo": ""
}