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Merge CSV files

Merge CSV tables in your chosen order, aligning headers or taking the union of columns, with local export.

All processing is local, without automatic storage or input uploads. Combined UTF-8 text/files: at most 2 MiB; each table has at most 5,000 data rows, 100 columns, 100,000 cells and 20,000 UTF-16 units per cell. Output including BOM: at most 2 MiB; each worker or file-reading operation has a 5-second deadline.

Delimiters are explicit; leading zeroes, spaces and line breaks inside cells remain. Blank rows are not dropped and uneven rows are not padded. A final line terminator is not an extra record. Original files stay unchanged.

Table 1

The first row contains unique, nonempty headers; matching is exact and case-sensitive.

Table 2

The first row contains unique, nonempty headers; matching is exact and case-sensitive.

Order follows the tables above, then each table’s rows. Strict mode allows reordered headers and realigns columns. Union keeps headers in first-seen order; duplicate rows are retained.

CSV quotes every cell and uses CRLF; downloads include a UTF-8 BOM, while copy does not. The system clipboard may normalize line breaks inside cells too; use the download to preserve their original line breaks. The default policy prefixes an apostrophe before potential leading =, +, -, @, tabs or line breaks, including headers and negative numbers. Only the export copy changes. Literal export can be interpreted as formulas by a spreadsheet application; review import-as-text settings.

How to use

Paste two tables or choose a local file for each, and set their delimiters. Add tables if needed and use the move buttons to order the batch. Choose matching header sets or their union, review the export policy and process. Review the preview, then copy or download the complete CSV.

Try an example

The first table has id,name and row 001,Amal; the second has name,id and row Ali,002. Strict merging produces id,name followed by 001,Amal and 002,Ali; the second file’s column order does not change which header each value belongs to.

Support & limits

Header matching is exact, including case and spaces. Strict mode allows reordered headers; union preserves first-seen header order and uses empty strings for missing columns. Duplicates, blank rows and spaces are not removed automatically. Uneven CSV and invalid quoting are rejected. Original files remain unchanged.

Common questions

Does the result include every table or only the preview page?

CSV quotes all cells and uses CRLF while preserving line breaks inside cells. Downloads include a UTF-8 BOM; copy does not. The system clipboard may normalize line breaks inside cells too; use the download to preserve their original line breaks. By default, formula-like cells, including headers and negative numbers, receive an apostrophe in the export copy only. Literal export leaves them unchanged, but a spreadsheet application may interpret them as formulas. Review import-as-text settings. The preview limits displayed rows and columns; copy and download include the complete result.

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