A client came to us with a seemingly simple request: remove all converted leads from the All Contacts list in SFMC. Their CRM sync had been running for two years and All Contacts had ballooned with Lead records that no longer existed in Salesforce. It was eating into their contact credits and slowing down automations.

Their developer had already tried using Subscriber.Remove() in a loop script. The script ran without errors. The contacts were still there. This is the first thing almost everyone tries, and it is the wrong tool for the job — and understanding exactly why it fails is what makes the correct approach make sense.

Contact Builder’s All Contacts list — once contacts are here, removing them requires the REST API, not the Core Library subscriber functions.

Why Subscriber.Remove() Does Not Actually Delete Contacts

Subscriber.Remove() from the Core SSJS library removes a subscriber from a specific list. That is all it does. It does not touch the All Contacts list, the contact data model, or any of the channel-specific contact records. The subscriber record in All Contacts remains completely intact after calling it.

Full contact deletion from All Contacts requires going through the Contacts REST API, specifically the DeleteByListReference endpoint. This is the only method that actually removes a contact from the SFMC contact data model across all apps — Email, MobileConnect, MobilePush, and all sendable Data Extensions. It is also asynchronous, which means the deletion is queued and processed in the background, sometimes taking several hours depending on volume.

What You Need Before Running This

Step 1: Identify the Contacts to Delete

Before anything else, you need to populate a sendable Data Extension with the SubscriberKeys of the contacts you want to remove. The REST API endpoint reads from this DE — it does not accept a dynamic query, it reads a pre-populated list.

For the most common use case — removing converted leads that no longer exist as Leads in Salesforce — the SQL query below identifies them. It uses the Salesforce ID prefix pattern to find Lead records (00Q prefix) in All Contacts that no longer have a corresponding record in the Leads synchronized DE:

/* Find Lead records in All Contacts that no longer exist
   in the Salesforce Leads sync DE.
   Salesforce Lead IDs start with '00Q'.
   Salesforce Contact IDs start with '003'.
   Adapt the JOIN to your own synced Lead/Contact DE names. */

SELECT
    ac.SubscriberKey

FROM _EnterableContacts ac

LEFT JOIN Lead_Salesforce lead
    ON ac.SubscriberKey = lead.Id

WHERE
    ac.SubscriberKey LIKE '00Q%'
    AND lead.Id IS NULL

Step 2: The SSJS Deletion Script

Once the staging DE is populated, this script authenticates against the Marketing Cloud REST API and fires the DeleteByListReference request. Drop it into an SSJS Script Activity in Automation Studio, schedule it to run after your SQL query populates the staging DE, and it handles the rest.

<script runat="server">
Platform.Load("Core", "1");

var clientID     = "YOUR_CLIENT_ID";
var clientSecret = "YOUR_CLIENT_SECRET";
var clientBase   = "YOUR_28_CHAR_SUBDOMAIN";
var deletionDEKey= "YOUR_DELETION_DE_EXTERNAL_KEY";

var contentType  = "application/json";
var accessToken  = "";
var operationID  = "";

try {
    var authUrl     = "https://" + clientBase + ".auth.marketingcloudapis.com/v2/token";
    var authPayload = Stringify({
        "grant_type":    "client_credentials",
        "client_id":     clientID,
        "client_secret": clientSecret
    });
    var authResponse = HTTP.Post(authUrl, contentType, authPayload);
    var authObj      = Platform.Function.ParseJSON(authResponse["Response"][0]);
    accessToken      = authObj.access_token;

    if (!accessToken) { Write("Authentication failed."); return; }

    var deleteUrl     = "https://" + clientBase
                      + ".rest.marketingcloudapis.com"
                      + "/contacts/v1/contacts/actions/delete?type=listReference";

    var deletePayload = Stringify({
        "deleteOperationType": "ContactAndAttributes",
        "targetList": {
            "listType": { "listTypeID": 3 },
            "listKey":  deletionDEKey
        },
        "deleteListWhenCompleted":         false,
        "deleteListContentsWhenCompleted": true
    });

    var headerNames  = ["Authorization"];
    var headerValues = ["Bearer " + accessToken];

    var deleteResult = HTTP.Post(deleteUrl, contentType, deletePayload, headerNames, headerValues);
    var resultObj = Platform.Function.ParseJSON(deleteResult["Response"][0]);
    operationID   = resultObj.operationID;
    Write("Deletion queued. OperationID: " + operationID);

} catch(ex) {
    Write("Error: " + Stringify(ex));
}
</script>

Frequently Asked Questions