Transformation

A Transformation is an engine that sits in front of every channel/destination. It sees every event you send to EdgeTag and can reshape it, drop it, or fan out additional events before the event reaches any individual channel.

Use a Transformation when you want to modify events already flowing through the channels EdgeTag ships with — for example, dropping PageView events from paid-media channels, enriching every Purchase with a server-side source field, hashing PII uniformly across channels, or emitting a Purchase_Facebook event when the user's last paid-media click was Facebook.

A Destination sends events to a new integration you're building from scratch. A Transformation reshapes events that are already going to existing channels. If you need to make outbound HTTP requests or store data, use a Destination.

The six execution levels

A Transformation consists of six files, one per execution level. Three run on the edge and three run in the browser, each at a different granularity:

Level	Edge file	Browser file	Runs
Root	tagRoot	clientTagRoot	Once per event, before channel routing
Channel	tagChannel	clientTagChannel	Once per provider channel (for example Facebook)
Instance	tagInstance	clientTagInstance	Once per provider instance (for example facebook||pixel1)

The rule of thumb: use root for rules that apply to all channels, channel for rules tied to a specific provider, and instance for rules tied to a specific pixel or account within a provider.

To set channel or instance settings, exit the Playground from full screen and select options that you would like.

What a Transformation can do

Every file returns an object that tells EdgeTag how to handle the event. Any combination of these four is valid:

• Modify the payload — return { payload: <modified> } to change the event before it reaches channels.

• Skip the event — return { skipEvent: true } to drop the event for this level (everywhere, for this channel, or for this instance).

• Emit additional events — return { additionalEvents: [<event>, ...] } to fan out extra events alongside the original.

• Update user data — return { user: <modified> } to change the PII attached to this event.

Transformations are pure event transforms — they don't make HTTP requests, don't write to storage, and don't touch the identity graph. If you need any of that, use a Destination.