OFFICE🔗Merge CSV
Multi-file UNION · header union
Vertically concatenates multiple CSV files (UNION). Headers are auto-merged as a union; missing columns are filled with empty strings. Column order follows the first appearance across all files. Excel locale encodings (UTF-8 / GBK / Shift_JIS / Big5 / EUC-KR, etc.) are auto-detected — override manually if needed; the download includes a UTF-8 BOM so Excel opens it correctly.
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Merge CSV files: vertical concat with header union and dedupe
The merge CSV use case is fixed: a monthly or per-branch export in the same shape (or a few columns apart) that has to become one master table. This tool concatenates CSVs vertically and takes the union of headers - if file A has a notes column and file B does not, the rows from B simply get an empty notes cell instead of failing the merge.
How to use: click Add CSV files, multi-select, then Merge, check the 10-row preview and download. Column order follows the first appearance of each column name across files.
Common pitfalls: encoding - a GBK or ANSI export may turn into mojibake after merging, so convert to UTF-8 with the encoding repair tool first; inconsistent column names are treated as two columns, so unify headers before merging; for multi-column dedupe use the Excel dedupe tool, which dedupes on any column combination and exports xlsx.
Related: CSV and Excel data tutorials.
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