DoH query values that can be passed on the command line for testing with curl can be obtained by encoding binary DNS messages into base64url, with trailing '='s removed. For example: $ perl bin/tests/system/fromhex.pl << EOF | base64url # Transaction ID 0001 # Standard query 0000 # Questions: 1, Additional: 0 0001 0000 0000 0000 # QNAME: example 07 6578616d706c65 00 # Type: SOA 0006 Class: IN 0001 EOF This produces the string "AAEAAAABAAAAAAAAB2V4YW1wbGUAAAbFrMonAAE=". With the trailing '=' removed, this can then be passed to curl: curl "https:///dns-query?dns=AAEAAAABAAAAAAAAB2V4YW1wbGUAAAbFrMonAAE"