Choose multiple CSV files, preserve the union of columns, review the merged row count, and download a combined copy locally.
Merge multiple CSV or TSV files locally with union or strict headers, optional deduplication, a source filename column, preview and download.
Use the header, dedupe and source-column options above, then inspect schema differences and sample rows before downloading the same previewed merge.
CSV has no universal schema or type system. Delimiter detection and type summaries are practical heuristics, while repairs create a new copy instead of silently altering the source. Excel conversion focuses on cell values and simple worksheets rather than promising perfect preservation of formulas, macros, charts, external links, formatting or every workbook feature.
Two CSV files can look similar while using different header names or column order. Preview the header union and per-file differences before export so values do not silently land under the wrong field.
Strict mode is appropriate when every file is expected to have the same schema. Union mode is safer for real-world exports with optional columns because missing cells can remain blank instead of forcing columns into the wrong positions.
Exact row deduplication removes byte-equivalent field sets after parsing. It does not identify near-duplicates, spelling variants, repeated customers with changed details or records that require a key-based business rule.
When several exports are combined, retaining the original filename can make later troubleshooting much easier. It lets you trace an unexpected row back to the input file without reopening every source manually.
The v12.75 preview reports file counts, header differences, row counts and a sample of the exact merged output. Check that evidence before downloading, especially when delimiters, quoting, embedded commas or missing columns are present.
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