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Classic retention

Also called N-day, Day-N or exact-day retention. How it is counted, a worked example, and what it can and cannot tell you.

Short answer

Classic retention is the share of an install cohort that opened the app on exactly Day N after installing. Also called N-day, Day-N or exact-day retention. In the sample app, the 1 Sep cohort's classic Day 7 is 16%.

What is classic retention?

Classic retention is the share of an install cohort that opened the app on exactly Day N after installing.

A user counts on Day N if they opened the app on exactly Day N. Activity on any other day does not count. Day 0 is the install day and never counts as a return; several opens on one day count once.

classic(N) = users active on Day N / installs in the cohort x 100

The same definition is used in Linkrunner's glossary entry on classic retention, so the numbers here line up with tools that follow it.

Figure 1

Worked example: ten users

Ten made-up users over 14 days, counted with the classic rule at Day 7. Shaded columns are the days that count.

	D0	1	2	3	4	5	6	7	8	9	10	11	12	13	14
User 1																counted
User 2																not counted
User 3																not counted
User 4																counted
User 5																not counted
User 6																not counted
User 7																not counted
User 8																not counted
User 9																counted
User 10																not counted

Classic Day 7: 3 of 10 = 30%

The same ten users at Day 7 under the other rules: rolling 60%; cumulative 80%. Try other days in the ten-users view.

Source: Sample data: a made-up app to show the method, not a benchmark.

How does classic retention behave across a cohort?

The 1 Sep cohort of the sample app, the only one observed to Day 14.

Day N	Users counted	Classic retention
Day 1	51 of 148	34%
Day 3	42 of 148	28%
Day 7	23 of 148	16%
Day 14	23 of 148	16%

Figure 2

Every cohort, counted as classic

Rows are install days, columns are days since install.

Install cohort	D1	D2	D3	D4	D5	D6	D7	D8	D9	D10	D11	D12	D13	D14
1 Sep Tue148 installs	34	23	28	24	19	16	16	16	27	18	8	17	15	16
2 Sep Wed152 installs	34	36	32	28	24	20	19	36	14	18	17	17	18
3 Sep Thu154 installs	41	30	23	27	27	23	38	18	13	18	13	13
4 Sep Fri142 installs	38	26	22	21	18	35	20	18	15	14	12
5 Sep Sat148 installs	36	27	26	26	39	20	16	12	12	16
6 Sep Sun249 installs	29	26	22	36	17	14	15	16	10
7 Sep Mon262 installs	29	20	39	16	17	16	13	12
8 Sep Tue278 installs	32	42	21	21	18	19	13
9 Sep Wed258 installs	52	25	20	19	17	14
10 Sep Thu266 installs	31	20	18	15	14

0%85%+not reached yet

Source: Sample data: a made-up app to show the method, not a benchmark.

Strengths

Fixed once Day N has passed, so a number in last month's report never changes.
The definition most published benchmarks use, so it is the fair one for outside comparison.
Shows calendar events clearly: a release or a push lights up one diagonal of the table.
Each point on the curve is the share of users active that day, which is what forecasts of active users need.

Traps

Punishes apps people use weekly or irregularly: a loyal user who skips the exact day is not counted.
Noisy day to day, especially on small cohorts and around weekends or campaigns.
A bump on one day (a push notification) can look like better users when it is a one-day event.

What can classic retention tell you?

What you can conclude

Whether one cohort was more active on a given day than another at the same age.
Whether a change on a specific day moved activity on that day (read the diagonal).
How your exact-day number compares with a published benchmark that uses the same definition.

What you can't

Whether a user has churned: absent on Day 7 does not mean gone.
How many users came back at least once (that is cumulative).
Anything from one small cohort on one day without checking its neighbours.

Compare with the other two

Questions

What is classic retention?

Classic retention is the share of an install cohort that opened the app on exactly Day N after installing. It is also called N-day or Day-N retention, and it is fixed once Day N has passed.

Is N-day retention the same as classic retention?

Yes. N-day, Day-N, exact-day and classic retention are names for the same rule: count users active on exactly the Nth day after install. Always check which day counts as Day 0 in your tool.

Why is classic retention lower than rolling or cumulative?

Classic only credits activity on one day. Rolling and cumulative both include that day plus other days, so they can never be lower than classic for the same cohort and Day N.

What is the difference between classic, rolling and cumulative retention?

Classic counts users active on exactly Day N. Rolling counts users active on Day N or any later day, and cumulative counts users active at least once from Day 1 to Day N. They use the same raw activity but answer different questions.

Why is my rolling retention higher than classic?

Rolling also counts users who skipped Day N but came back later, so it can never be lower than classic. The gap grows the longer a cohort has been observed, because late returns keep adding to it.

What is cumulative retention?

Cumulative retention is the share of an install cohort that opened the app at least once between Day 1 and Day N. It never falls as N grows and it is fixed once Day N has passed, which makes it a good activation measure.