CSV Merge / VLOOKUP Tool
Free online CSV merge and VLOOKUP tool. No upload required.
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What is CSV Merge / VLOOKUP Tool?
The CSV Merge / VLOOKUP Tool joins two CSV datasets on a shared key column, exactly like a spreadsheet VLOOKUP or a SQL left/inner join. Paste a main table and a lookup table, pick the matching columns, and get a merged CSV with the extra fields appended — computed fully in your browser.
Key Benefits
- No spreadsheet app or VLOOKUP formulas needed
- Works on any size of pasted CSV, right in the browser
- Data never leaves your machine — 100% client-side
- Matched/unmatched row statistics at a glance
- Fine control over columns, duplicates, and name conflicts
Common Use Cases
- •Enriching an export of users or orders with data from another system
- •Bringing department, product, or pricing details into a report CSV
- •Deduplicating work that would otherwise need Excel VLOOKUP or INDEX/MATCH
- •Joining offline datasets when no database or SQL access is available
- •Preparing merged CSVs for imports into CRMs, ERPs, or BI tools
How to Use the CSV Merge / VLOOKUP Tool
- Paste both CSVs: Paste your main CSV (the rows you want to keep) on the left and the lookup CSV (the data to bring in) on the right. Quoted fields are handled automatically.
- Choose the key columns: Pick the matching column in each file — for example id in the main CSV and dept_id in the lookup CSV. Header names from your data appear in the dropdowns.
- Set join options: Choose left join to keep every main row or inner join for matches only. Select which lookup columns to append and how duplicate keys and name collisions are handled.
- Copy or download the merged CSV: Review the matched/unmatched statistics and the green-highlighted joined columns in the preview table, then copy the merged CSV to your clipboard or download it as a file.
Key Features
- Left join keeps all main rows; inner join keeps matched rows only
- Pick the key column in each file from real header names
- Append only the lookup columns you choose
- Handle duplicate lookup keys: first, last, or merged values
- Rename, skip, or keep columns with clashing names
- Case-insensitive and whitespace-trim key matching
Frequently Asked Questions
How is this different from a spreadsheet VLOOKUP?
It works the same way conceptually — you match rows on a shared key and bring extra columns across — but it runs entirely in your browser on pasted CSV text. There is no row limit from a spreadsheet app, no formula writing, and nothing is uploaded to a server.
What happens when the lookup CSV has duplicate keys?
You control the behavior with the multiple-match setting: use the first matching row, use the last one, or merge all distinct values into a single cell separated by semicolons. The tool also shows a warning with the count of duplicate keys found.
What is the difference between left join and inner join?
A left join keeps every row from the main CSV and leaves the appended columns blank when no match is found. An inner join outputs only the rows that matched, which is useful for cleaning a dataset down to known keys.
How are matching keys compared?
Keys are compared as text after optional trimming of surrounding whitespace, with an optional case-insensitive toggle. The lookup key column itself is never appended to the output — only the columns you select.