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Why are my SKAN conversion values null?

A SKAN postback only carries a conversion value if the app set one and Apple's privacy tier allows it. Check the postback fields first, then your update calls.

Your answers

Every path

All questions and diagnoses

The full decision tree, if you'd rather read it than click through.

Does the postback have did-win set to false?
- Yes, did-win is false
  - Diagnosis: Non-winning postback. Apple's documentation says non-winning postbacks never contain a conversion value, so a null value with did-win false is expected.
- No, it is a winning postback
  - Which postback is missing its value?
    - The first postback
      - How many digits is the source identifier in that postback?
        2 digits
        Does the postback carry a coarse value of low, medium or high?
        Yes, a coarse value only
        Diagnosis: Crowd anonymity tier 1: coarse value only. At tier 1 Apple sends a 2-digit source identifier and a coarse value instead of the fine value, because the campaign does not have enough installs for a higher tier.
        No value at all
        Diagnosis: Crowd anonymity tier 0, or no update call. At tier 0 Apple sends only a 2-digit source identifier with no conversion value, and the same postback shape appears if the app never set a value.
        3 or 4 digits
        Does the app call updatePostbackConversionValue on first launch and when key events happen?
        No, or not sure
        Diagnosis: The app never sets a conversion value. Apple only includes a conversion value if the app provides one, so if the update method is not called, the postback arrives without it.
        Yes
        Is every fine value you send a whole number from 0 to 63?
        No, or not sure
        Diagnosis: Fine value out of range. Apple's fine value is a 6-bit number from 0 to 63, and any value outside that range returns an invalid conversion value error and is ignored.
        Yes
        Diagnosis: Updates arrive after the window closed or was locked. Each SKAN 4 window accepts updates only while it is open, and once you lock a window, further updates in that window are ignored.
    - The second or third postback
      - Does the app update the coarse value during days 3 to 7 and 8 to 35, using the method that takes a coarse value?
        No, or we use the older method
        Diagnosis: No coarse updates in later windows. The second and third postbacks carry only coarse values, and the older update method works only in the first window, so later postbacks stay empty unless you call the newer method.
        Yes
        Diagnosis: Updates arrive after the window closed or was locked. Each SKAN 4 window accepts updates only while it is open, and once you lock a window, further updates in that window are ignored.

Related symptoms

iOS SKANSecond and third SKAN postbacks arrive days lateApple adds a random delay of 24 to 144 hours after the second and third windows close.→iOS SKANNo SKAN postbacks arriving at allThe app never registers the install with SKAN, or the postbacks are still inside Apple's random delay.→iOS SKANOnly one SKAN postback, never the second or thirdThe install falls into tier 0, the ad was signed with SKAN 3 or earlier, or the app uses the older update method.→iOS SKANSKAN postbacks with a null conversion valueThe postback is non-winning, falls into a low crowd anonymity tier, or the app never set a value.→

FAQ

Common questions

Why is my SKAN conversion value null?

Usually because the postback is non-winning, the campaign falls into a low crowd anonymity tier, or the app never set a value. Apple only includes a value when the app provides one and the tier allows it.

What is crowd anonymity in SKAN?

Crowd anonymity is how Apple decides how much detail a postback carries, based on how many installs share the same app, source and country. Lower tiers get shorter source identifiers and coarse or no conversion values.

Do second and third SKAN postbacks have fine values?

No. Apple ignores fine values after the first window, so the second and third postbacks carry only a coarse value of low, medium or high.

How can I test SKAN conversion values quickly?

Install an Apple testing profile on the device. Apple says it cuts the delay from install to postback from 24 to 48 hours down to about 5 to 10 minutes.

What is mobile attribution?

Mobile attribution is the process of crediting each app install or in-app event to the ad, link or channel that drove it. A mobile measurement partner (MMP) does this across all your channels so each install is counted once.

Why do ad networks report more installs than my MMP?

Each network counts every install it touched within its own windows, including views, while an MMP gives each install to a single source. Adding the networks' numbers together therefore overstates real installs.