Sending server-to-server clicks to AppsFlyer

At a glance: Provide attribution link clicks via S2S for users that are sent directly to the app stores.

Attribution link flow


Don't accumulate S2S clicks and send them in bulk. Send S2S clicks immediately after the user clicks an ad or a banner. Otherwise, AppsFlyer might not attribute the install, which could result in revenue loss for the partner. AppsFlyer relies on clicks for the attribution flow. This means AppsFlyer must log clicks on ads to attribute an install.

When a user clicks on a banner or an ad, the following takes place:

  1. The user is redirected to AppsFlyer
  2. AppsFlyer logs the click
  3. AppsFlyer redirects the user to the app store
  4. The user installs the app
  5. AppsFlyer attributes the install

Sending S2S clicks to AppsFlyer

If a partner wants to send the user directly to the store, the partner must send the click to AppsFlyer using server-to-server (S2S). Redirecting the user to the store makes for a better user experience by reducing the number of redirections.

The S2S click URL is similar to the regular click URL. The only difference is that the S2S URL should include the parameter &redirect=false. This parameter lets AppsFlyer know that this is an S2S click and that the partner is responsible for redirecting the user that clicked. 

S2S clicks with referrer or device ID

Attribution of installs based on S2S clicks relies on the same matching methods described in the AppsFlyer attribution model.

The recommended and most accurate methods are Install referrer (Android only) or device ID matching. Aggregated Advanced Privacy and Probabilistic modeling are supported but should be used if other methods are unavailable.

Attribution methods available


In cases where a partner redirects the user to the store, the partner can append the Google Play as well as other third-party stores Referrer to the link that they send to the store and also on the S2S click that they send to AppsFlyer.

This allows AppsFlyer to use the referrer as the attribution method for S2S clicks.

The ID (referrer) that the partner generates must be unique and must adhere to the following:

  • The prefix should be the name of the partner
  • The ID must include the unique transaction ID per click

Example: NetworkA_1234567

The store URL should contain the transaction ID under the referrer parameter.


The partner should append the referrer on the S2S click that it sends to AppsFlyer. The referrer is appended to the af_ref parameter. See examples that follow.

Device ID

The device ID can be added to the click URL using any of the following:


  • It is best to give priority to the Android advertising ID (GAID). 
  • If you can't send GAID, use the Android ID instead. Hash the Android ID using SHA1.

Android Identifiers

  • &android_id={android_id} 
  • &sha1_android_id={sha1_android_id}
  • &advertising_id={advertising_id}
  • &sha1_advertising_id={sha1_advertising_id}

 iOS identifiers.

  • &idfa={idfa}
  • &sha1_idfa={sha1_idfa}

Probabilistic modeling

To implement Probabilistic modeling attribution, you must send the parameters detailed in this section via URL parameters or HTTP request headers.

Parameter Description
af_lang Device language and locale

It's recommended to provide both language and locale.

For example, "en-US".

Extraction methods

iOS (Objective-C) Android (Java)
NSString *language = [[NSLocale preferredLanguages] objectAtIndex:0];

This parameter lets AppsFlyer know that this is an S2S click and that the partner is responsible for redirecting the user that clicked.

Must be set to false.

af_ua User-Agent must be sent as:
  1. URL parameter (URL-encoded)
  2. HTTP request header (unencoded)

The User-Agent should be identical in both the URL parameter and the HTTP header.


Device IP address

Best option: If available, provide the device IP under the af_ip parameter.

Next option: If available, AppsFlyer will use the IP in X-Forwarded-For.

S2S click URL examples

When you send S2S clicks, make sure the URL is encoded.

The URL examples below are decoded for readability.


With device ID

With Google play referrer


With device ID********?pid=media_source&c=campaign_name

Timing S2S clicks

S2S clicks should be sent in real-time. This means that the partner sends the S2S clicks immediately after it sends the user to the relevant app store.

If the S2S click is not sent in real-time, AppsFlyer might not attribute the install.

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