What a product journal is for
Answering "why did that number change?" with facts, not stories. One timeline the whole team trusts. When the weekly report lands and retention is down, you don't want a meeting where everyone has a theory. You want a timeline that shows what shipped, what launched, what broke. The journal is that timeline. It turns "why did that happen?" from a debate into a look-up. You look. You see. You know.
The journal is also the link between "we did something" and "the number moved." Without it, you see the number and you wonder. With it, you see the number and you see the deploy, or the campaign, or the pricing change. Cause and effect. That connection is what makes the journal valuable. It's not just a log. It's the thing that makes your metrics interpretable. When the number moves, the journal tells you why. When you ship a change, the journal is where you record it so that when the number moves, the cause is visible. One timeline. One source of truth. The whole team trusts it because everyone can add to it and everyone can see it.
What to log
Ship a feature? Log it. Change price? Log it. Launch a campaign or have an outage? Log it. Date and short description. Link to more detail if needed. The bar is low. If it could plausibly move a key metric, it belongs in the journal. Releases. Pricing changes. Campaigns. Incidents. Big onboarding changes. New paywall. Anything that could show up in the numbers. Log it when it happens. Don't wait. Don't batch at the end of the week. The moment something goes out that could move a metric, add an entry. If the entry isn't there when the weekly report lands, the cause is invisible. Log at ship time or launch time. That's the habit. Ship it, log it. Launch it, log it. Then when the number moves, the journal has the answer.
Keep entries short. One line is often enough. "v2.1 shipped: new onboarding flow." "Campaign X launched." "Pricing updated: Pro plan." The goal is to have a scan-able timeline. If every entry is a paragraph, nobody will scan it. Short. Clear. Enough to remember what happened. The journal is not a spec. It's a log.
What to skip
Don't log every tiny tweak. Log things that could plausibly move a key metric. A copy change on a button might not move the needle. A new step in the onboarding flow might. Use judgment. When in doubt, log it. You can always ignore it later. It's worse to miss something and then wonder why the number moved. If you're not sure, add the entry. The cost of a few extra entries is low. The cost of missing the cause of a big move is high.
Don't log internal stuff that doesn't touch the product. "Had a planning meeting." "Updated the roadmap." Those don't move metrics. Users don't see them. The journal is for things that could show up in the numbers. Product changes. Launches. Incidents. External factors that might affect usage. Keep the bar at "could this move a metric we care about?" If yes, log it. If no, skip it.
Making it a habit
Log at ship time or launch time. If it's in the journal when the weekly report lands, cause and effect stay visible. The habit is: we ship something, we log it. We launch something, we log it. No "I'll do it later." Later doesn't happen. The journal only works if it's current. So the rule is simple. Something goes out that could move a metric? Add an entry. Right then. Make it part of the ship process. Make it part of the launch process. When it's automatic, the journal becomes useful. When it's optional, it stays empty. Empty journal, no cause and effect. Full journal, clear cause and effect. The habit is the feature.
