Q5 for App Marketers: The Flight Ends Long Before the Data Lands
Q5 is the stretch between Christmas and the middle of January, a period that sits outside the four-quarter calendar everyone budgets against. It has a following for two structural reasons, both of which hold without a statistic attached.
The first is that a meaningful share of fourth-quarter demand is tied to pre-Christmas delivery deadlines. When those deadlines pass, the competitive pressure that portion of the market was applying stops with them, and whoever is still bidding faces a thinner field.
Second, devices are unwrapped, activated, handed down, or set up for the first time in those three weeks, and a device in that state has no apps on it.
What almost every Q5 guide leaves out is the part that decides whether you can act on any of it: on iOS, a Q5 flight can still be reporting on February 15, and most teams sit down to judge the flight in the second week of January.
Everything below is drawn from Apple's own developer documentation, with the relevant page linked in each section.
When a Q5 flight actually finishes reporting
Take a flight running December 26 to January 5, which is 11 days and a normal Q5 shape.
Apple's conversion window documentation sets out three windows. They run days 0 to 2, days 3 to 7, and days 8 to 35, and the clock starts when the user first launches the app, not when the campaign runs or when the install happens. After each window closes, the system waits a random interval before sending: 24 to 48 hours for the first postback, and 24 to 144 hours for the second and third.
Apply those windows and delays to a single user who first launches on the opening day of the flight, December 26:
A user who first launches on December 26, the flight's opening day
Conversion windowWindow closesPostback arrivesFirst, days 0 to 2December 28December 29 to 30Second, days 3 to 7January 2January 3 to 8Third, days 8 to 35January 30January 31 to February 5
Now the same for a user who first launches on the flight's final day, January 5:
A user who first launches on January 5, the flight's final day
Conversion windowWindow closesPostback arrivesFirst, days 0 to 2January 7January 8 to 9Second, days 3 to 7January 12January 13 to 18Third, days 8 to 35February 9February 10 to 15
So the flight ends on January 5, and for a user who first launches that day, the last postback can arrive as late as February 15. That is 41 days after the flight's final day. Users who click during the flight but install later run later still, because a click stays eligible for 30 days.
Read that timeline against the date you were going to review the flight. Budgets reset in January, and the Q5 review usually happens in the second week. Take January 12 as the review date. The opening-day cohort, first launched December 26, has returned its first two postbacks. The closing-day cohort, first launched on January 5, has returned only the first, which covers days 0 to 2.
You would be judging a flight on the first two days of behavior from its newest users, most of whom first launched the app during a holiday.
There is a second twist that makes the early read misleading rather than merely incomplete. The fine-grained conversion value is available only in the first postback. The second and third postbacks carry a coarse value. So the richest signal arrives first and describes the shortest period, and every postback after it is coarser by design. If an install falls into the lowest postback data tier, the system sends only the first postback and no conversion value at all.
One more easy-to-miss condition: receiving the second and third postbacks isn't automatic. Apple states that the advertised app has to call the conversion value update method during each window for the later postbacks to be sent at all. An app that calls the method on day one and never again produces one postback per install, two to four days after each user's first launch, and nothing after that.
December clicks beat Q5 views
The second measurement problem in Q5 has nothing to do with waiting.
Apple's attribution documentation sets how long an install can still be attributed to an ad: 24 hours after a view-through ad, and 30 days after a click-through ad.
A 30-day install window reaches far back from Q5. An install on January 3 can still be won by a click from December 4, and an install on January 10 by a click from December 11. Every click your fourth-quarter campaigns bought in the back half of December is still live through the entire Q5 window, competing for the installs your Q5 budget is producing.
That December click does not compete on equal terms, either. Apple's sorting rules put click-through ads ahead of view-through ads before recency is considered at all, and sort by timestamp only within each group. A click is not a tiebreaker applied at the end; it is the first sort key. So a December click that a user half-remembers outranks a Q5 view-through impression served an hour before the install. A more recent Q5 click, by contrast, still beats the December one.
Two consequences worth planning around.
If you buy view-through inventory in Q5, you are buying impressions that expire in 24 hours and that lose the attribution contest to any click in the preceding month. The channel can be working and still lose the credit, though it does receive a nonwinning postback, which is a signal without credit.
Your December campaigns will also be credited with installs that arrive during Q5, whether or not Q5 budget produced the demand. Some of what they appear to have produced in the first week of January is Q5 demand landing against an older click.
Why the Q4 comparison is the wrong one
The instinct is to put Q5 performance next to Q4 and see whether the cheaper window delivered. It is the wrong comparison, for a reason that has nothing to do with media.
Q5 changes the population, not just the price. A cohort acquired in the three weeks after Christmas over-selects for people setting up a new device, people with unusual amounts of unstructured time, and, in many categories, people who did not choose the device themselves. If the window over-selects that way, then retention curves, purchase behavior, and session patterns from that cohort are a poor read on the rest of the year, and they don't match the fourth quarter's patterns either.
That cuts both ways, which is why the point is worth stating outright. A Q5 cohort can look exceptional in week one and ordinary by week six. It can also look thin in week one and compound, because a new device has no competing apps on it yet.
The honest comparison is Q5 against Q5, year over year, on the same read date. A holdout inside the Q5 window, or a full incrementality test, is the only version that answers this year's question instead of last year's.
Why none of this arithmetic reaches connected TV
Q5 is also when the big screen is busiest, and connected TV is the one channel discussed here to which none of the arithmetic above applies, because none of the apparatus exists.
Apple lists AdAttributionKit as available on iOS 17.4 or later and Mac Catalyst 17.4 or later. tvOS is not on the list. The framework that resolves the attribution contest does not run on the device the ad played on, which is the structural reason CTV-to-mobile measurement stays probabilistic no matter how the campaign is set up, and the reason CTV installs arrive late and land in organic.
In a period when the household is at home, and the television is on, that gap is worth knowing in advance instead of discovering it in the January report. A CTV flight in Q5 will be undercounted by the same dashboard that is already two conversion windows short on the newest Q5 cohort. Plan it on an incrementality read rather than an attributed one.
What to decide before December 26
Four things need deciding, and all of them are cheaper to settle now than in January.
Set two read dates, not one. Pick an early checkpoint for spend and delivery decisions, and a separate, later date for the performance verdict. Given a flight ending January 5, the verdict date is February 15, or it is not a verdict. Write both dates down before anything launches.
Decide what the comparison is. The candidates are last year's same window, a holdout inside this one, or an incrementality test. Agreeing on it in December costs a meeting. Agreeing on it in January, after someone has seen a chart they like, costs you control of the decision.
Confirm the app updates its conversion value in all three windows. This is one message to whoever maintains the build, and the answer determines whether you get one postback per install or three. It is the difference between knowing how a Q5 cohort behaved and knowing only that it arrived.
Separate the December click tail from the Q5 buy in your own reporting. Or at least know the tail is there. If you are judging Q5 on attributed installs in the first half of January, some of that is December's.
If you want the full mechanics behind the windows, tiers, and delays, our post on what AdAttributionKit changed for advertisers covers the windows, tiers, and delays this post assumes, including the settings in your own app that change which impression wins.
The short version of all of it: Q5 is real, and the Q5 window is genuinely less crowded than the quarter before it. The January verdict isn't real. Plan the read dates with the same care you give the buy, and the window becomes something you can actually learn from rather than something you argue about in a meeting on January 12.
FAQ
What is Q5 in marketing?
The period between Christmas and roughly mid-January, which falls outside the standard four-quarter calendar. It draws attention for two structural reasons: many advertisers buying against the retail season stop on Christmas Day, which thins the auction, and a large number of devices are activated or set up for the first time over the same three weeks.
How long does it take to get full results from a Q5 campaign on iOS?
Longer than the Q5 window itself. Apple's three conversion windows run days 0 to 2, days 3 to 7, and days 8 to 35 from the user's first app launch, and each postback is held for a random interval after its window closes: 24 to 48 hours for the first, and 24 to 144 hours for the second and third. For a user who first launches on January 5, the last postback can arrive as late as February 15.
Why do Q5 campaigns look worse in early January than they actually are?
Because the review usually happens before the data arrives. In the second week of January, the newest cohort has returned only its first postback, which covers days 0 to 2. The fine-grained conversion value appears only in that first postback, so the richest signal covers the shortest period, and later windows arrive with a coarse value weeks later.
Can December campaigns take credit for January installs?
Yes. Apple allows an install to be attributed to a click-through ad for 30 days, so clicks served in December remain eligible through the whole Q5 window. Click-through ads also take precedence over view-through ads in Apple's sorting before recency is considered, so a December click can outrank a Q5 view served an hour before the install. A more recent Q5 click still beats it.
Should you compare Q5 against Q4?
Not as a performance verdict. The populations differ: a cohort acquired in the three weeks after Christmas over-selects for new-device setup and unusual amounts of free time, so its retention, purchase, and session patterns are a poor read on fourth-quarter patterns or on the rest of the year. Compare Q5 to the same window last year on the same read date, or run a holdout or an incrementality test inside the window.
Does the attribution arithmetic apply to connected TV?
No. None of the measurement apparatus exists there. Apple lists AdAttributionKit as available on iOS 17.4 or later and Mac Catalyst 17.4 or later, with tvOS absent from the list, so a CTV impression produces no postback at all and the connection to a mobile install stays probabilistic. Plan a Q5 CTV flight on an incrementality read rather than an attributed one.
