Key activation metric and how to find yours

A key activation metric is the early action, or small set of actions, that new users take and that goes with them still being customers months later. PostHog defines activation metrics as "a set of actions a new user performs that correlate with greater retention". Finding yours means comparing retention across candidate actions, then rebuilding onboarding to get more people to the best one. It needs enough signups and enough time to see retention, so it suits a product that already has a few months of users.

How to do it

1. Decide what retained means. PostHog's definition is a company still using the product 3 months after starting. Pick yours and write it down.
2. List events that might hook users: created the first project, connected a data source, invited a teammate. PostHog started from a big list like this.
3. Make 5 to 10 candidate groups of 3 to 5 events each. Include counts, because some users need to do something more than once. PostHog compared "watched 5 replays" with "watched 1 replay".
4. For each group, calculate retention for the users who did it and compare it with retention across all users. The group with the highest retention is your candidate.
5. Rebuild the first session around it: defaults, a checklist, the first email. The goal is to get more new users to that action quickly.
6. Test it. Send half of new users through the new onboarding and compare retention. If the users you pushed to the action do not stick around better, the original pattern was selection (committed users do more of everything).

When activation turns into a drop in usage later, see reduce activity churn.

Examples

PostHog (session replay). In a post dated Nov 28, 2024, PostHog says it tested many event groups and found that watching 5 or more replays and setting a replay filter at least once gave the highest retention. It also found that inviting teammates did not predict that users stuck around, and concluded that working on it is not the best use of its time. PostHog says it has 8+ products and had to do this work per product.

Facebook. Chamath Palihapitiya, a former Facebook growth executive, said in a talk in October 2012: "The single biggest thing we realized was to get any individual to 7 friends in 10 days." This is his account from a talk, and TechCrunch describes his team as helping put Facebook "on the path to one billion users". Facebook's underlying data is not public.

When it backfires

• Correlation, not cause. Heavy users do more of everything, so a gap between users who did X and users who did not does not prove X drives retention. Step 6 above is the check.
• Too little data. With a few dozen signups, any pattern is noise. Wait, or use the metric only as a hypothesis.
• One metric for every segment. PostHog needed a different metric for each of its products. A single number across different customer types hides that.
• Forcing the action. Nagging users toward the magic number without helping them get value can raise the activation rate and leave retention flat.
• It drifts. If the product changes, recheck that the action still predicts retention.

Questions people ask

What is an activation metric? The action or actions that predict a user will stay, found by comparing retention across candidates.

What is the activation rate? The share of new users who complete the activation action within a set time, such as 7 days.

How do I double my activation rate? Find the step between signup and the activation action where most people drop off, and fix that step first. Measure again before touching the next one.

Sources

• PostHog: how we found our activation metric, read Oct 8, 2026
• TechCrunch: Chamath Palihapitiya on growth hacking, read Oct 8, 2026
• Startup Archive: Chamath Palihapitiya on Facebook's growth principles, read Oct 8, 2026