Merge CSV Files Online Free — Combine Multiple Datasets
Two Ways to Merge CSVs
Append (vertical merge): stack files on top of each other. Useful when each file is a time period (Jan sales + Feb sales + Mar sales). Columns must match. Join (horizontal merge): combine files by a shared key column (like customer_id or product_sku). Similar to SQL JOIN — inner, left, and full outer joins supported.
Common Use Cases
Monthly report consolidation: append 12 monthly CSV exports into one annual dataset. CRM data enrichment: join a customer list CSV with a product purchase CSV on customer_id to see what each customer bought. A/B test result merging: combine variant A and variant B result CSVs for unified analysis.
Column Matching and Deduplication
When appending files with different column sets, the tool aligns columns by header name and fills missing values with empty cells. Duplicate header detection warns you before merging. Deduplication option removes rows where all columns match exactly — useful for removing double-counted entries in exported reports.
Frequently Asked Questions
Merge CSV files free
Stack or join CSV files in your browser — no formulas, no scripting.
Open CSV Merger