Join CSV Files by Key Column
Join two CSV files on a common key column, like VLOOKUP or a SQL JOIN
Join two CSV files on a shared key column — an ID, email, SKU, or any value both files have in common. It works like a VLOOKUP in Excel or a JOIN in SQL, but without formulas or a database: upload both files, pick the key column in each, and download the combined result.
Choose how unmatched rows are handled: an inner join keeps only rows found in both files, a left join keeps everything from the first file, and right or full outer joins keep the rest. Both files are processed locally in your browser, so customer lists and other sensitive data are never uploaded.
Drop your file here or click to upload
Supports CSV, TSV, TXT files up to 100MB
Drop your file here or click to upload
Supports CSV, TSV, TXT files up to 100MB
How to Use
- Upload the two CSV files you want to join
- Pick the key column in each file (like an ID or email)
- Choose the join type: inner, left, right, or full outer
- Preview the joined table and download the combined CSV
Features
- Inner, left, right, and full outer joins
- Match on any key column in each file (IDs, emails, SKUs)
- VLOOKUP-style first-match semantics for duplicate keys
- Instant preview of the joined result
- Handles files with different columns and row order
- Private by design — both files stay in your browser
Use Cases
- Add customer details from a CRM export to an orders file
- Enrich a mailing list with attributes from another system
- Match survey responses to a participant roster by email
- Combine product data with inventory counts by SKU
Frequently Asked Questions
How do I merge two CSV files based on a common column?
Upload both files, select the matching key column in each (for example an ID or email address), and choose a join type. Rows with the same key value are combined into one row with the columns from both files.
What is the difference between inner, left, right, and full outer joins?
An inner join keeps only rows whose key exists in both files. A left join keeps every row from the first file, filling blanks where the second has no match. A right join is the reverse, and a full outer join keeps all rows from both files.
What happens if the key appears more than once in the second file?
The first matching row is used, the same way Excel VLOOKUP behaves. Deduplicate the lookup file first with the CSV Dedupe tool if you need one-to-one matching.
Is this the same as merging CSV files?
Merging usually means stacking rows from files with the same columns — use the CSV Merger for that. Joining combines columns from two files side by side by matching rows on a key.
Is CSV Joiner free to use?
Yes, completely free with no limits. No signup or download required.
Is my data private when joining CSV files?
Absolutely. Both files are processed in your browser and never uploaded, stored, or logged — safe for sensitive data.