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CSV Merger

Merge several CSVs into one in your browser. Paste them separated by a blank line — the first block's header is kept and the rest are stacked beneath it.

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Quick Answer

Paste two or more CSVs, each separated by a blank line, and get one combined CSV. The tool keeps the header from the first block and appends the data rows from every block beneath it. Rows are stacked by position, so the blocks should share the same columns in the same order. It runs in your browser.

What the CSV Merger Does

This stacks several CSVs into one. You paste each CSV as a block, separated by a blank line. The tool takes the header from the first block and then appends the data rows from every block, skipping each block's own header.

The rows are combined by position, not matched by column name, so the blocks should have the same columns in the same order for a clean result.

How It Works

Paste your CSVs into one box, separating each with a blank line.

The first block's header row becomes the header of the merged file.

Every block's data rows are appended in order, with each block's own first line skipped as its header. Copy or download the merged CSV — all in your browser.

Data source & conversion logic

  1. Split into blocks. The input is divided into blocks wherever there is a blank line.
  2. Take the first header. The header row of the first block becomes the merged header.
  3. Append the data rows. Every block's remaining rows are added in order, skipping each block's own header.
  4. Output one CSV. The combined rows are written as a single CSV to copy or download.

How the merge works

Header is taken from the FIRST block only Each block's first row is treated as its header and skipped All remaining rows are appended in order Rows are stacked by position, not matched by column name
Worked example
Two CSVs with the same name,age columns, pasted with a blank line between, merge into one CSV under the first header — Alice from the first block and Bob from the second.

Because rows are stacked by position, a block whose columns are in a different order would land its values under the wrong headers.

Privacy

Your CSV data is processed entirely in your browser — there is no server and nothing is uploaded.

The data never leaves your device, so even sensitive records stay private.

No account, no stored copy; the conversion is gone when you close the tab.

Technical Details

InputMultiple CSVs, blank-line separated
HeaderFrom the first block only
Block headersFirst row of each skipped
CombineBy position, not by name
OutputOne CSV (.csv)
Best forSame columns, same order
Processing100% in-browser

Standards & references

  • RFC 4180 (CSV) — The parser understands quoted fields, so values with commas stay intact across the merge.
  • Positional append — Rows are stacked by column position; there is no matching or alignment by header name.

Accuracy & Limitations

The header comes from the first block only. Every block's own first row is treated as a header and skipped, so all blocks should include a header line.

Rows are stacked by position, not matched by column name. If a later block has its columns in a different order, or different columns, its values land under the wrong headers. Make sure all blocks share the same columns in the same order.

Blocks are separated by a blank line. A stray blank line inside one CSV would split it into two blocks, so keep each CSV contiguous.

The parser handles quoted fields, so a value containing a comma or a line break is preserved as it moves into the merged file.

Real-World Use Cases

Combine exports

Stack several CSV exports with the same columns into one file.

Monthly to yearly

Merge monthly CSVs into a single combined dataset.

Gather samples

Join CSVs collected from different sources that share a schema.

Rebuild a split file

Recombine parts that were split apart earlier.

When to use it — and when not to

Good for

  • CSVs that share the same columns in the same order
  • Stacking exports into one file
  • Quick row-wise concatenation

Not the best choice for

  • Blocks with different column orders or names
  • Joining on a key (a database-style join)
  • Files too large to paste

If your CSVs have different column orders, align them in a spreadsheet first. For a key-based join rather than a stack, use a spreadsheet or database.

Frequently Asked Questions

How do I separate the CSVs?
Put a blank line between each CSV block in the input box. The blank line is the boundary.
Whose header is used?
The first block's header. Every other block's first row is treated as its header and skipped.
Does it match columns by name?
No. Rows are stacked by position, so the blocks should keep the same columns in the same order.
What if a later block has different columns?
Its values are placed under the first block's headers by position, which can be wrong if the order or columns differ.
Do all blocks need a header?
Yes. Each block's first row is skipped as a header, so include one in every block.
What if there is a blank line inside one CSV?
It would be read as a block boundary and split that CSV in two. Keep each CSV contiguous, with no internal blank lines.
Does it remove duplicate rows?
No. Every data row from every block is appended as-is, including duplicates.
Does it handle quoted fields?
Yes. A value containing a comma is preserved as one field during the merge.
What format do I get?
One merged CSV (.csv) you can copy or download.
Can I merge more than two?
Yes. Paste as many blocks as you like, each separated by a blank line.
Is my data uploaded?
No. The merge runs entirely in your browser.
How do I split a CSV back up?
Use the CSV splitter to break a file into smaller parts.

References

Combines multiple CSV blocks (separated by a blank line) into one: it keeps the header from the first block and appends the data rows of every block beneath it. Rows are stacked by position, so the blocks should share the same columns in the same order. Runs in your browser.

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