Q: What should I record BEFORE we migrate, so I can prove what happened?

Q: What should I record BEFORE we migrate, so I can prove what happened?

Love this question — almost nobody does it, and then they can't tell normal dip from disaster. Here's your baseline kit.

Short answer: snapshot rankings, traffic, and the full crawl while the old site is still live.

Long answer, capture now:
— Full Screaming Frog crawl: every URL, status, title, meta, H1, canonical, word count. Save the file.
— GSC export: clicks, impressions, position by page and query, last 16 months.
— Analytics: organic sessions and conversions by landing page, same window.
— Your top 100 ranking keywords and positions from any rank tracker.
— Server log sample showing which URLs bots actually hit.

Next step: store all of it dated and untouched. Two weeks post-launch, this is the only thing that tells you signal from noise.