Marketing · Guide
How to clean a CSV for ad platform uploads
Audience uploads to Google Customer Match, Meta Custom Audiences, and LinkedIn Matched Audiences fail in predictable ways. Most are caused by formatting issues you can fix in two minutes — if you know what to look for.
Last reviewed: April 2026
The pre-upload checklist
- UTF-8 encoding without BOM. Excel often saves UTF-8 with BOM, which breaks some parsers.
- One header row, exactly as the platform expects (e.g. ‘email’ or ‘Email’ — match the platform's spec).
- No empty rows or trailing blank lines.
- Trim leading/trailing whitespace from every cell.
- Lowercase email addresses before hashing (if hashing is required).
- Remove duplicate rows on the matching key (usually email or phone).
Phone number formatting
Most platforms require E.164 format (+14155551234). Strip spaces, dashes, parentheses. If your source data has mixed formats, normalise before upload — partial matches don't get fixed retroactively.
Hashed vs raw uploads
Some endpoints require SHA-256 hashed values. Lowercase and trim before hashing — "Alice@Example.com " and "alice@example.com" hash to different values and won't match.
Quick cleanup
Paste a messy CSV into the CSV Audience List Cleaner to trim every cell, normalise headers, and dedupe in one step.
Tools mentioned
Further reading
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