Currently we have  REST API functionality for creating space exports only by using XML format. We need to have Rest API to create space/site exports by using HTML format.

Workaround

1. The Confluence CLI provides such functionality, but it is a paid third-party add-on. The above functionality would be important to automate migration/backup tasks for administrators.
2. Although deprecated, you may still use the RPC-API to export the entire Space - see the examples below.
   • Confluence JSON-RPC APIs
   • Remote Confluence methods
   • Remote API Specification for PDF export

Export a Space to HTML.

USRNAME=admin
USRPWD=password
CONFBASEURL=http://127.0.0.1:8090/confluence
SPACE_KEY=SPACEKEY

curl -s \
    --user $USRNAME:$USRPWD \
    -H "Content-Type: application/json" \
    -H "Accept: application/json" \
    -X POST \
    -d '{ "jsonrpc" : "2.0", "method" : "exportSpace", "params" : ["'${SPACE_KEY}'", "TYPE_HTML", "true"], "id": 7 }' \
    ${CONFBASEURL}'/rpc/json-rpc/confluenceservice-v2?os_authType=basic'

Space import

For possible workarounds on importing spaces, please also check this KB article: Confluence Space Import Via Scripting Tools