CSV Merge Tool Free
Combine up to 5 CSV datasets into one. Stack rows vertically, optionally add a source column to track origin, preview the combined result, and download. Handles mismatched columns by filling missing fields with empty values. Runs entirely in your browser.
CSV 1
CSV 2
Merged Result
Preview shows up to 20 rows
Pro — file upload, join on key column, unlimited inputs, column reorder, API
API access · Priority queue · Team workspace
How It Works
Paste Your CSV Files
Paste up to 5 CSV datasets into the separate input panels. Click Load Sample to populate two CSV inputs with complementary employee datasets — same columns but different employees — a clear example of the vertical stack merge. Use "Add another CSV" to add more input panels if you have more than two files to merge.
Set Options & Merge
Choose the output delimiter for the merged CSV. Enable "Add source column" to append a _source column (CSV 1, CSV 2, etc.) so you can trace which input each row came from after merging — invaluable for data reconciliation. Toggle duplicate removal to automatically deduplicate rows that appear in multiple inputs. Click Merge to combine.
Preview & Download
The merged data appears in a preview table showing up to 20 rows. The stats bar shows total rows and columns. Copy the merged CSV to clipboard or download as a .csv file. If the input CSVs have different columns, the output uses all unique column names as headers and fills missing values with empty fields so the merged file is always well-formed and importable.
CSV Merge Features
Smart vertical stacking with column alignment and source tracking
Vertical Row Stacking
All CSV inputs are stacked vertically — rows from CSV 1, then CSV 2, then CSV 3, and so on. A single header row from the union of all column names appears at the top. This is equivalent to SQL UNION ALL. It is the standard way to combine monthly exports, regional data, or paginated API results that all share the same schema into one complete dataset for analysis.
Mismatched Column Handling
If the input CSVs have different sets of columns (for example, one has a "department" column and another does not), the merged output includes all unique column names from all inputs. Rows from a CSV that lacks a particular column get an empty string in that column. This makes it safe to merge exports from different time periods where the schema evolved slightly between exports.
Source Column Tracking
The "_source" column appends the label "CSV 1", "CSV 2", etc. to every row, identifying which input file each row came from. This is essential for data reconciliation — after merging sales data from multiple regions, you can filter by _source to see region-specific totals alongside the combined view. Disable this column if you want a clean merged output without provenance metadata.
Duplicate Row Removal
When the deduplication option is enabled, rows that appear identically across multiple CSV inputs are deduplicated — only the first occurrence is kept. Comparison is done on the full row content (excluding the _source column if present). Useful when merging overlapping datasets where the same records may exist in multiple source files due to date-range overlaps or backup exports.
Live Preview Table
After merging, the first 20 rows of the combined result are shown in a formatted HTML table. Column headers are highlighted in orange. This lets you verify that columns aligned correctly, that the source column is working as expected, and that no data corruption occurred before downloading the full merged file. The stats bar shows total row and column counts.
100% Private
All merging runs in your browser — no CSV data is uploaded or transmitted to any server. This makes it safe to merge exports from CRMs, databases, analytics platforms, and other business systems that contain customer records, financial data, employee information, or proprietary data that cannot be shared with external services for processing.
Free vs Pro
| Feature | Free | Pro |
|---|---|---|
| Number of CSV inputs | Up to 5 | Unlimited |
| Source column tracking | ||
| File upload support | — | |
| Join on key column (SQL JOIN) | — | |
| Column reorder & rename | — | |
| REST API access | — |
Frequently Asked Questions
Merging (also called stacking or concatenation) combines CSVs by adding all rows from each file one after another — equivalent to SQL UNION ALL. All files should have the same columns (or at least similar ones). Joining combines CSVs by matching rows based on a shared key column — equivalent to SQL JOIN. For example, joining customer.csv and orders.csv on a "customer_id" column. This tool does merging; join support is a Pro feature.
The merged output uses the union of all column names from all input CSVs as the header row. Rows from a CSV that is missing certain columns will have empty values in those columns. This handles the common case where CSVs exported at different times have slightly different schemas — newer exports may have additional columns that weren't present in older exports, and the merge tool handles this gracefully without errors.
When "Remove duplicate rows" is enabled, each row is compared by its complete cell content (joined as a string key) against all previously seen rows. The first occurrence is kept and subsequent identical rows are removed. Note that the _source column is excluded from duplicate comparison — only the actual data fields are compared. This means a row appearing in both CSV 1 and CSV 2 with identical data values will be deduplicated even though their _source values differ.
The free tool supports up to 5 CSV inputs. To merge more than 5, you can merge in batches — merge the first 5, download the merged result, then merge that result with the next batch. Alternatively, upgrade to Pro for unlimited inputs and file upload support, which is more practical for merging dozens of monthly or regional CSV exports in a single operation.
Yes — each CSV input is independently parsed with auto-detection of its delimiter (comma, semicolon, tab, or pipe). This means you can merge CSV files with different delimiters — for example, a comma-separated export from one system and a semicolon-separated export from a European Excel locale. The output is written with the single delimiter you select in the "Output Delimiter" dropdown.
No — all merging runs in your browser. None of your CSV data is uploaded to, processed by, or stored on any server. Each input is parsed in browser memory and the merged result is produced locally. This makes the tool safe for merging exports from databases, CRMs, HR systems, and any other source containing sensitive business or personal data that must not leave your device.