Where SSJS Runs

CloudPages, Email, Automation Studio, JSON Code Resources — the full list of SSJS execution contexts and their differences.

SSJS executes in several different contexts within Salesforce Marketing Cloud, each with different capabilities and constraints.

CloudPages (Landing Pages)

CloudPages is the most flexible SSJS environment. A landing page is a publicly accessible URL hosted by SFMC.

Capabilities:

• Full request/response access (Platform.Request.*, Platform.Response.*)
• Read query strings, POST bodies, cookies, headers
• Set response headers, cookies, redirect
• Make external HTTP calls
• Full Data Extension CRUD

Limitations:

• DataExtension.Rows.Retrieve() does not work on CloudPages — use Platform.Function.LookupRows() instead
• Requests time out (no documented limit, but ~30s is a practical ceiling for external calls)

<script runat="server">
Platform.Load("core", "1.1.5");
var method = Platform.Request.Method; // "GET" or "POST"
Write("<p>Request method: " + method + "</p>");
</script>

JSON Code Resources

A special CloudPages type that sets Content-Type: application/json. Perfect for building simple API endpoints:

<script runat="server">
Platform.Load("core", "1.1.5");
Platform.Response.SetResponseHeader("Content-Type", "application/json");

var result = { status: "ok", timestamp: Platform.Function.Now() };
Write(Stringify(result));
</script>

You cannot write HTML and JSON in the same resource — the first Write() determines the content type behavior. Set the header explicitly at the top.

Email (Precompile)

SSJS in emails runs during precompile — when SFMC personalizes the email for each subscriber before sending. This is the most constrained environment.

Limitations:

• No request/response access (Platform.Request.* returns empty values)
• No Platform.Response.*
• Significant performance penalty compared to AMPscript — prefer AMPscript for data lookups
• Short execution window — keep logic minimal
• WSProxy works but is slower per-send than AMPscript equivalents

Valid use cases in email:

• Complex conditional logic that AMPscript can’t express cleanly
• JSON manipulation
• Custom function definitions for reuse

<script runat="server">
var firstName = Platform.Function.Lookup("Subscribers", "FirstName", "SubscriberKey", _subscriberKey);
var displayName = firstName ? firstName : "Subscriber";
Variable.SetValue("@displayName", displayName);
</script>
%%=v(@displayName)=%%

Automation Studio (Script Activities)

Script Activities let you run SSJS as a step in an Automation. This is how SSJS is used for scheduled batch processing.

Capabilities:

• Full SOAP API access via WSProxy
• Data Extension operations
• No request/response (not a web context)
• Hard 30-minute timeout per execution

Practical patterns:

• Batch-process rows in chunks to stay under the timeout
• Log progress to a Data Extension
• Use Platform.Function.Now() and date math to track elapsed time

<script runat="server">
Platform.Load("core", "1.1.5");

var startTime = new Date();
var maxMinutes = 25; // Leave 5-minute buffer

var proxy = new WSProxy();
var results = proxy.retrieve("DataExtension", ["CustomerKey", "Name"]);

var processed = 0;
for (var i = 0; i < results.Results.length; i++) {
    // Check elapsed time
    var elapsed = (new Date() - startTime) / 60000;
    if (elapsed > maxMinutes) { break; }

    // Process each item...
    processed++;
}

Write("Processed: " + processed + " items");
</script>

Triggered Send (Email)

Similar to email precompile. SSJS runs when a triggered send fires for a subscriber.

Note: Platform.Request.* is not available in triggered send context.

MobileConnect (SMS)

SSJS can run in MobileConnect context for SMS personalization, with significant limitations. Most data operations work, but HTTP and some response functions do not.

Summary Table

Context	Request/Response	HTTP Calls	Platform.Load	WSProxy	Rows.Retrieve
CloudPage	✅ Full	✅	✅	✅	❌ Use LookupRows
JSON Code Resource	✅	✅	✅	✅	❌
Email (precompile)	❌	✅	✅	✅ (slow)	✅
Automation Studio	❌	✅	✅	✅	✅
Triggered Send	❌	✅	✅	✅	✅
MobileConnect	Partial	❌	✅	✅	✅

→ Next: Embedding SSJS