How to use the merge or split csv files
- Choose Merge several CSV files into one or Split one CSV file into smaller files.
- To merge, add your files and put them in order. Choose the separator or leave it on automatic, say whether the first row is a header, and decide whether to match columns by header name when files differ. You can add a column with the source file name.
- To split, add one file, choose rows per file or the number of files, enter the amount, and keep the header row in every part if you wish.
- Press the button. A merge saves merged.csv and a preview appears. A split saves a ZIP of numbered files such as sales-part-01.csv.
Merging three files
Suppose two files have the header id, name, city and a third has name, id, zip. Merged by header name, the result has the header id, name, city, zip. The rows of the first two files get an empty zip, and the row from the third file, Zed with id 5 and zip 98101, gets an empty city and its values in the right columns: 5, Zed, empty, 98101.
To split a file with 10 data rows into parts of 4 rows each, you get three files holding 4, 4 and 2 data rows, each starting with the header. Asking for 3 files gives the same result because each part holds the rows divided by the count, rounded up. Asking for 6 files of 10 rows gives 5 files of 2 rows.
How the files are read
The reader follows the common CSV rules. A value can be wrapped in double quotes, which allows it to contain separators, line breaks and quotes written twice. A quote that is never closed is reported with the file name so you can fix it. Completely blank lines are dropped, and a byte order mark at the start of the first file is kept on the output so spreadsheet programs still show accented characters correctly.
Text is read as UTF-8. If a file was saved in a different encoding, some characters may look wrong, and the tool warns you when it sees such characters.
Choosing how to merge
Matching by header name is the safest way to combine files whose columns are in different orders or that have extra columns. If you turn it off, rows are simply stacked by position under the header of the first file. Use that when files have no matching names or when you want the position to decide.
Large files take time and memory, so merging is limited to 40 MB in total. For converting or checking a CSV, use the CSV to JSON converter, the CSV validator or CSV to SQL, and to compare two lists use compare two lists.
Assumptions and limits
- The same separator is used for all files in one merge. Mixed separators need to be fixed first.
- If a file has two columns with the same header name, matching by name is refused and you can stack by position instead.
- Quoting is applied only where needed, so the output can look slightly different from the input while holding the same values.
- At most 50 files, 25 MB each, are merged, and a split makes at most 500 files.
Frequently asked questions
How do I combine several CSV files into one?
Add the files, keep the header option on, and press Merge. Rows are stacked under one header, and columns are matched by name when the files differ.
How do I split a big CSV so it opens in a spreadsheet?
Choose the split option, enter how many rows each file should hold, keep the header in every file, and download the ZIP. Each part is a complete CSV that opens on its own.
What if my files have columns in a different order?
Leave matching by header name on. The merged file uses the columns of the first file and adds new ones at the end, and each value goes to the column with its name.
Will quotes and commas inside values survive?
Yes. Values with separators, quotes or line breaks are read correctly and written back in quotes where required, so their content does not change.