The symptom
Performance had fallen sharply and stayed down. Nobody on the client side had touched the account. There was no seasonal explanation, no obvious competitor entry, and the landing pages were unchanged.
That combination points at something automated, because accounts do not degrade quietly on their own.
What the change history showed
Change history records automated changes alongside manual ones, and it is the first place to look when performance moves without explanation. Filter by change type and the picture usually becomes obvious within minutes.
In this case the log showed keywords removed as redundant, match types broadened, and new keywords added automatically. Each individual change looks reasonable in isolation. Together they replaced a controlled account with a much broader one that spent the same budget across far less relevant traffic.
Why auto-apply causes this
Recommendations optimise toward Google's objectives, which overlap with yours but are not identical. Broader matching increases eligible impressions, which is good for the auction and frequently bad for a tightly managed account with negative keyword discipline.
The setting is on by default, which means most advertisers have consented without deciding. Turning it off is a two-minute change and it is the first thing we do on any account we take over.
How to check your own account
- Open Tools, then Change history, and set the date range to cover the period performance changed
- Filter by change type and look specifically for automated entries
- Cross-reference the dates against your performance graph
- Go to Recommendations, then auto-apply settings, and switch off anything you did not consciously choose
Key takeaways
- Auto-apply is enabled by default and does make changes you did not approve
- Change history records automated changes with dates, which usually explains the drop
- Switching it off takes two minutes and should be done on every account