UtilityDock

Free browser-based CSV tool

CSV Merge

Merge CSV files locally in seconds. Everything stays in your browser.

Your files never leave your computer.All processing happens locally inside your browser.

  • Append compatible files in their original row order
  • Inner join records using one exact shared key
  • Preview matches, exclusions, and format differences
1

Upload File A

File A determines the merged file's encoding, delimiter, and line endings.

Drop File A here

or use the file browser

2

Upload File B

File B is read locally and compared with File A before merging.

Drop File B here

or use the file browser

What CSV merging is

Combine compatible exports without sending them to a server

CSV merging creates one table from two source files. You can stack records that share the same structure or combine fields from records that share a unique identifier. UtilityDock validates both files before creating a new download.

Append vs join

Choose the operation that matches your data

ModeUse it whenOutput
AppendBoth files have identical headersFile A rows followed by File B rows
Join by keyBoth files share one unique identifierOnly matching records with combined columns

Common workflows

Bring related exports into one useful file

  • Append monthly exports with the same columns
  • Combine regional order files into one report
  • Join customer details to an order export by customer ID
  • Add inventory status to a product list by SKU
  • Match campaign results to contacts by record ID
  • Combine two clean batches after reviewing a CSV Split

Examples

Predictable results from two small rules

File AFile BResult
500 January orders600 February orders1,100 appended rows
Products keyed by SKUPrices keyed by SKUMatching products with price columns
3 customer IDs2 matching IDs2 inner-joined rows; unmatched rows reported

CSV Toolkit

Inspect, prepare, and clean CSV files locally

CSV SplitDivide one CSV by rows, file count, or column value.CSV FilterKeep rows that match one clear condition.CSV Column ReorderArrange columns while preserving every row.CSV Column RemoverRemove fields and download a focused copy.CSV Delimiter ConverterConvert comma, semicolon, tab, and pipe files.CSV Encoding & Delimiter DetectorInspect structure and import risks.CSV Column MapperRename and normalize headers.CSV Header Inspector & ValidatorCatch blank, duplicate, and risky headers.CSV Duplicate Finder & RemoverFind repeated rows and create a clean copy.
Browse the CSV Toolkit

FAQ

Questions about merging CSV files

Does UtilityDock upload or store my CSV files?

No. Your files never leave your computer. Parsing, validation, merging, preview, and download creation all happen locally inside your browser.

What is the difference between append and join?

Append places File B's rows after File A and requires matching headers. Join by key combines columns from records whose selected key value appears exactly once in both files.

Which joins are supported?

Version 1 performs a simple inner join using one shared column. It does not support left, right, outer, fuzzy, multiple-key, or many-to-many joins.

What happens to rows without a matching key?

An inner join excludes unmatched rows from the merged output. UtilityDock reports their combined count before download.

Why are duplicate join keys blocked?

Duplicate keys can create one-to-many or many-to-many results. Version 1 requires unique nonblank keys so every match remains predictable.

Which file controls the output format?

File A controls the output encoding, BOM behavior, delimiter, and line endings. Differences in File B are reported before merging.