Tracking Link vs Postback: What Goes Where

What is a postback?

A postback is the server-to-server request an MMP sends to a partner when an attributed conversion happens, filling the partner's URL template with the click ID and the conversion details.

Tracking link (click link): the URL the user passes through on the way to the store. It carries the click into the MMP.

Postback URL: a URL template the partner gives the advertiser's MMP. It carries the conversion back out.

Direction is the easiest way to remember it: the tracking link flows from you to the MMP at click time, and the postback flows from the MMP to you after the install or event.

Side by side

The two meet at the click ID: you send it out on the link and the postback brings it home.

Which values belong on which?

Anything that exists at click time goes on the tracking link; anything that only exists after a conversion goes in the postback.

On the click link:

• Campaign identifier (pid and c on AppsFlyer, ~campaign on Branch)
• Your click ID
• Sub-IDs and passthrough values
• Device IDs, where the MMP documents them

Postback only, never on the click link:

• Revenue, sale amount and currency
• Event names
• Secret or postback keys
• Checksums such as crc

On a click link these values are ignored or stored as meaningless text, and a secret on a click link is exposed to anyone who sees the URL. The generator on the home page flags postback-only values if you add them to a click link.

Worked example: a postback template

A postback URL is your receiver's address with the MMP's macros where the values should go. An install postback template might look like this:

https://postback.example-network.com/install?click={click_id}&pub={sub_publisher}&ts={install_time}

And an event postback with revenue:

https://postback.example-network.com/event?click={click_id}&ev={event_name}&rev={revenue}&cur={currency}

The macro names in braces are placeholders here. Each MMP has its own list, so copy the exact names from the advertiser's MMP rather than from this example.

Postback macros by MMP

• Adjust: callbacks are set up with the advertiser. Placeholders include {gps_adid}, {idfa}, {idfv} and {adid}, a label on the link comes back through {label}, and callback URLs must be percent-encoded as one value. See the Adjust link format.
• Tenjin: callback macros include the channel's click_id and site_id, the six tenjin_parameter passthrough values, and an impression flag that is 1 for view-through and 0 for a click.
• AppMetrica: any click link parameter can be forwarded to the postback by name in braces.
• Linkrunner: macros are lowercase in single braces, such as {click_id}, {event_name}, {revenue} and {s2}, and are sent as HTTP GET requests. Its postbacks and macros documentation lists the full set.

Questions to settle before you build the receiver

• Which events will send a postback, and who maps them?
• Are values URL-encoded, and what arrives when the MMP has no value for a macro?
• What format are timestamps in, and is revenue in major or minor units?
• Which IP addresses will postbacks come from, if your firewall needs them?
• Can the same postback arrive twice? If so, deduplicate on the click ID plus the event name before you count or pay.

Postback macro syntax is MMP-specific in the same way click macros are platform-specific; the macros guide covers the click side. On the advertiser's side, postbacks also feed ad networks and ROAS reporting, which this chapter on events, postbacks and ROAS explains.