From scraped list to ad audience

A scraped or purchased list is not an audience yet. Between the list and a paid campaign sit a few steps that are easy to get wrong.

The steps

1. Import contacts from a CSV and reject rows that don’t parse.
2. Enrich missing fields from a data provider.
3. Normalize and hash emails before they leave your system.
4. Upload to the ad platform as a custom audience.
5. Poll until the platform reports the audience as ready.

Rules worth enforcing

• Decode untrusted input once at the boundary, then use the validated value.
• Keep personal data out of analytics tables and logs.
• Treat a platform as ready only after reading its state back.

Why code beats a spreadsheet here

Each step can fail on its own and be retried without redoing the others. When an upload is rejected, you want the failing row and the reason, not a vague error on a final screen.