CSV Merger

How to use CSV Merger

1. Select the CSV files to combine.
2. Check the detected headers and normalise any near-duplicates first.
3. Merge and download the combined file.
4. Columns are matched by header name, not by position.
5. Headers differing in case or whitespace become separate columns — normalise them first.
6. Files are read locally; nothing is uploaded.

Header matching is what makes this safe

Stacking files by position breaks the moment one export has its columns in a different order, and the failure is silent — emails land in the phone column and nobody notices until someone tries to use the data. Matching on header names means a file with the same fields in any order merges correctly, and a file with an extra field gets a column with blanks elsewhere rather than corrupting the rows.

Check the headers before you merge

Near-identical headers are the usual problem: ‘Email’ against ‘email’ against ‘E-mail’, or a trailing space that nobody can see. Each variant becomes its own column, and the result looks merged while being split. Normalise the headers across your files first — lowercase, trimmed, consistent spelling — which takes a minute and prevents an afternoon of reconciliation.

Merging is not deduplicating

Combining two exports that overlap gives you duplicate rows, and removing them needs a decision about what makes two rows the same. Identical across every column is easy; identical email address with different names is a judgement call about which record wins. Decide that before merging rather than discovering it afterwards, and keep the source files so you can redo it differently.