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CSV guide

How to Merge Multiple CSV Files with Different Columns

Appending raw lines works only when every file has identical headers and no valid field contains a newline. A safer merge parses each source independently and aligns its cells before writing the combined file.

Merge CSV files

Try this guide’s example here

Step by step

  1. Choose all input files in one selection.
  2. Use header union when files may add columns, or intersection when only shared columns should remain.
  3. Enable the source filename column when the output needs provenance.
  4. Review missing values and diagnostics before downloading the merged CSV.

Check the result

  • Confirm that each output header appears once and that values from every input file land under the intended column.
  • Filter by the optional source filename column and compare a few records with each original file.
  • Review the final row count: it should normally equal the sum of data rows in all inputs unless a file was rejected.

Common pitfalls

  • Position-based alignment can put values under the wrong header when files use different column orders.
  • Header spelling and whitespace must match for name-based alignment.
  • A multiline quoted value is one CSV record even though it occupies more than one physical line.

Try the example on this page

Choose Try sample to load this guide’s synthetic data. Adjust the settings, inspect the result and export it here. You can also choose your own file for local processing.

CSV export options
Drop a file, paste data, load a CORS-enabled URL, or try the sample.
Rows0
Columns0
EncodingAuto
DelimiterAuto
Issue groups0

Open a data file to start

The parser runs off the main thread. Once loaded, you can search, sort, validate, repair and export without an account.

Original samples: merge-east.csvmerge-west.csv

Check expected outcomes and file checksums

Related CSV guides

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