Duaer

Online tools

Merge Excel and CSV files online (columns matched by header)

A free Duaer tool: pick several Excel or CSV files, match columns by header name, and get one table with an optional source-file column. No upload.

How to use it

  1. Select every file to merge at once (hold Ctrl or Cmd), or drop them into the box above together.
  2. Check the preview to make sure the columns line up.
  3. Click "Download .xlsx" or "Download .csv".

Merge rules

  • The first row of each table is its header, and columns with the same name are stacked together. A column that only one file has stays blank for the others. Column order follows first appearance.
  • Only the first sheet of each file is read by default; tick "Merge every sheet of every file" to include all sheets.
  • The "Source file" column holds the file name (or "file / sheet" when every sheet is merged) so you can trace each row.
  • Fully empty rows are skipped. CSV files are read as UTF-8 or GBK automatically, and you can mix Excel and CSV.

Automate it in Duaer

Merging the same set of files every month? In Duaer, collect them with a form, read each with Extract from File, and write the combined table with Convert to File › Convert to XLSX. Steps are in Merge Excel files.

Questions

Can it merge files whose columns are in a different order?

Yes. The Duaer merge tool matches columns by header name, not position, so order does not matter.

What if headers are spelled differently, like "Amount" and "Amount (USD)"?

The Duaer merge tool only matches identical headers. Rename them first, or combine the two columns in Excel after merging.

How many files can I merge at once?

Duaer sets no limit; your browser memory does. Dozens of ordinary spreadsheets usually work.

In this section

File conversion

Free file converters from Duaer

Free Duaer tools for spreadsheets and data files: convert formats, merge, split, remove duplicates, fix encodings, and format JSON. Everything runs in your browser and no file is uploaded.

File conversion

Split an Excel table by column online (one sheet per value)

A free Duaer tool: pick a column such as department, region, or store, and get one sheet per value, or download any group as CSV. No upload.

File conversion

Remove duplicate rows from Excel or CSV online

A free Duaer tool: open an Excel or CSV file, pick the columns that define a duplicate, keep the first row, optionally ignore case and spaces, and see how many rows were removed. No upload.

File conversion

CSV to Excel converter (free, no upload)

A free Duaer tool that turns CSV into .xlsx in your browser. It detects UTF-8 or GBK, keeps long IDs as text, and never uploads the file.

Office tasks

Merge several Excel files into one sheet with Duaer

In Duaer, upload several xlsx files, read every row, tag each with its source file, remove duplicates, and export one combined sheet. No formulas and no AI credits.