Simulation

Simulation runs a single file in an isolated sandbox against a realistic sample event, captures the result, and shows you exactly what EdgeTag would do with the event — without anything reaching production.

What gets run

When you click Simulate, Playground:

1. Takes the code from the file you selected.

2. Injects your Secrets into params.variables (scoped to edge vs. browser — see Secrets).

3. Runs the file against the current sample event.

4. Captures logs, the return object, and any thrown error.

Because Transformations don't make HTTP requests, the captured output is mostly about the return object — the thing that tells EdgeTag how to change the event.

Sample events

Every session starts with three pre-populated sample events you can switch between:

• Purchase — a full purchase with two line items, user PII, and realistic providerData (an fbclid, a gclid, UTM parameters).

• PageView — a page view with a name and category.

• AddToCart — a single-item add-to-cart.

The sample also includes a platform (SHOPIFY), userCustomData, and hostData (userAgent, ip, country, and so on).

What you see

The simulation output has three sections:

• Return — the object your function returned: { payload?, user?, additionalEvents?, skipEvent? }. This is the most important part of the output for a Transformation.

• Logs — everything you wrote with params.logger.log(...) or params.logger.error(...).

• Error — if your code threw, the error message and stack.

Sensitive values are redacted automatically: any header or body key matching authorization, token, api-key, api_key, secret, password, or cookie is replaced with [REDACTED] before being shown.

Reading the result

Three quick patterns for reading simulation output:

Confirm you dropped an event. The return should be exactly { "skipEvent": true }:

Simulation output

{
  "result": { "skipEvent": true },
  "logs": []
}

Confirm your payload enrichment. Compare result.payload.data against the input to see the fields you added:

Simulation output

{
  "result": {
    "payload": {
      "eventName": "Purchase",
      "data": {
        "orderId": "ORD-2024-001234",
        "value": 149.99,
        "currency": "USD",
        "source": "website",
        "valueUSD": 149.99
      }
    }
  }
}

Confirm your fan-out. additionalEvents should contain the extra events you emitted:

Simulation output

{
  "result": {
    "additionalEvents": [
      {
        "eventName": "Purchase_Facebook",
        "eventId": "evt_123abc456def",
        "data": { "orderId": "ORD-2024-001234", "value": 149.99 }
      }
    ]
  }
}

Simulating each level independently

Each level is simulated independently. tagRoot runs once; tagChannel and tagInstance are invoked per provider and need params.providerId to be set. The result you see is specifically the return of the level you selected — to test a tagChannel rule that only fires for Facebook, select the tagChannel file and make sure the sample includes providerId: 'facebook'.

Simulate after every meaningful change. Because Transformations are pure event transforms, the return object is a complete description of what your rule does — if the return looks right, the rule is right.