Q: I changed my attribution model and now last month's channel numbers look different — is that a bug?

Q: I changed my attribution model and now last month's channel numbers look different — is that a bug?

A: No — GA4 attribution changes apply retroactively to your reports, which surprises everyone.
— The setting lives in Admin → Attribution settings. Switching from last-click to data-driven (or changing the lookback window) recomputes credit across historical conversions.
— This reshuffles channel reports but never alters Explorations that use event-scoped data or your raw event counts.
— The lookback window (default 90 days for acquisition, 30 for other) also reweights older touchpoints.

Note the change date so you can explain the step in your trend lines.

TL;DR: Attribution edits reapply to past data — expect channel reports to shift.

Got a GA4 question? Drop it 👇