Use the free CSV File Merger below: your data never leaves your browser — all work happens on your device, and nothing is uploaded to any server.
What this tool does
Data that belongs together often arrives apart: one CSV per month, one per region, one per branch. This free CSV File Merger stacks up to five CSV files into one table in your browser with the PapaParse parser. Headers are aligned across files, so a column that appears in one file but not another still lands in the right place, with blanks where a file had no such column.
Choose your files, press Merge files, and the combined CSV appears in the output box, ready to download. All work is local: your files are never uploaded to any server.
How to use it
Press Choose CSV files and select up to five files at once. Press Merge files. The status line reports how many files merged and how many data rows the result holds. Download the merged CSV with the button below the output box.
Try a sample if you want to see header alignment in action: two small tables with partly overlapping columns merge into one table where the shared column lines up and the unshared columns are filled with blanks where needed.
How header alignment works
The merger first builds the union of all headers, in the order they first appear. Then it rewrites every row against that full header list, placing each value under its own header and leaving blanks elsewhere. That is what makes merging safe: a file whose columns arrive in a different order still merges correctly, because placement follows the header name, not the position.
Exact header spelling matters. “Email” and “E-mail” are different headers to the merger, and both will appear in the result. Before merging files from different sources, normalise header names in a text editor so matching columns share one spelling.
Common merging jobs
Monthly reports are the most common: twelve monthly exports become one yearly file for analysis. Regional sales, branch inventories, and survey waves follow the same pattern. Merging also helps when a system exports one file per category and the analysis needs a single table.
Another use is repair: when a large export was split for transport, merging the parts restores the original file, provided the header was repeated in each part. If headers differ between parts, check the merged result carefully before treating it as the original.
Tips for clean results
First, confirm all files use the same delimiter and encoding. A semicolon-delimited file merged with comma-delimited files produces one giant first column for that file. Second, check for a header row in every file; a file without one contributes its first data row as headers, which corrupts the merge. Third, compare row counts: the merged data rows must equal the sum of the input data rows.
Fourth, scan the merged result for columns that should have matched but did not, usually betrayed by two near-identical headers or a column that is blank for a whole file’s rows. Fixing the header spelling and merging again takes seconds and saves hours of confused analysis later.
Frequently asked questions
Are my files uploaded? No. PapaParse reads each file in your browser, and the merge happens locally. Nothing leaves your device.
What if files have different columns? The result contains the union of all columns. Rows from a file without a given column get a blank in that column.
What if files have columns in different orders? Values still land under the correct header, because placement follows header names, not positions.
Can I merge more than five files? Merge in rounds: merge five, download the result, then merge that result with the next batch. The union logic works the same at each round.