Change the HTTP Host header and DNS record

The following origin rule overrides the HTTP Host header to hr-server.example.com for all requests with a URI path starting with /hr-app/. It also overrides the DNS record to the same hostname.

The Host header override only updates the header value; the DNS record override will handle the rerouting of incoming requests. For more information on these overrides, refer to Available settings.

Dashboard

Expression when using the Expression Builder:

Field	Operator	Value
URI Path	starts with	/hr-app/

Expression when using the Expression Editor:

(starts_with(http.request.uri.path, "/hr-app/"))

Value after Host Header > Rewrite to:

hr-server.example.com

Value after DNS Record > Override to:

hr-server.example.com

API

The following example sets the rules of an existing phase ruleset ($RULESET_ID) to a single origin rule — overriding the Host header of incoming requests and the resolved DNS record — using the Update a zone ruleset operation. The response will contain the complete definition of the ruleset you updated.

Required API token permissions

At least one of the following token permissions is required:

• Response Compression Write
• Config Settings Write
• Dynamic URL Redirects Write
• Cache Settings Write
• Custom Errors Write
• Origin Write
• Managed headers Write
• Zone Transform Rules Write
• Mass URL Redirects Write
• Magic Firewall Write
• L4 DDoS Managed Ruleset Write
• HTTP DDoS Managed Ruleset Write
• Sanitize Write
• Transform Rules Write
• Select Configuration Write
• Bot Management Write
• Zone WAF Write
• Account WAF Write
• Account Rulesets Write
• Logs Write
• Logs Write

Update a zone ruleset

curl "https://api.cloudflare.com/client/v4/zones/$ZONE_ID/rulesets/$RULESET_ID" \
  --request PUT \
  --header "Authorization: Bearer $CLOUDFLARE_API_TOKEN" \
  --json '{
    "rules": [
        {
            "expression": "starts_with(http.request.uri.path, \"/hr-app/\")",
            "description": "Origin rule for the company HR application",
            "action": "route",
            "action_parameters": {
                "host_header": "hr-server.example.com",
                "origin": {
                    "host": "hr-server.example.com"
                }
            }
        }
    ]
  }'

{
  "result": {
    "id": "<RULESET_ID>",
    "name": "Origin Rules ruleset",
    "description": "Zone-level ruleset that will execute origin rules.",
    "kind": "zone",
    "version": "2",
    "rules": [
      {
        "id": "<RULE_ID>",
        "version": "1",
        "action": "route",
        "action_parameters": {
          "host_header": "hr-server.example.com",
          "origin": {
            "host": "hr-server.example.com"
          }
        },
        "expression": "starts_with(http.request.uri.path, \"/hr-app/\")",
        "description": "Origin rule for the company HR application",
        "last_updated": "2022-06-03T14:42:04.219025Z",
        "ref": "<RULE_REF>"
      }
    ],
    "last_updated": "2022-06-03T14:42:04.219025Z",
    "phase": "http_request_origin"
  },
  "success": true,
  "errors": [],
  "messages": []
}