Keyjoin Spreadsheet Merge

Merge two spreadsheets on a messy ID column, or stack many exports with drifting columns, and see every match decision.

Keyjoin Spreadsheet Merge does the VLOOKUP job on whole files. It joins two CSV or Excel files on a key column and cleans the keys the way real exports break them: extra spaces, upper/lower case, leading zeros (C00123 vs C123), Excel number formatting (12345.0, 1.2345E+05), dashes and spaces inside IDs, and look-alike characters. Each clean-up is counted and shown, so you can see how many rows needed it. Rows that still do not match get a likely reason and the closest key. It also stacks up to 24 monthly exports into one table when the column names drift (Amount vs Amt, Date vs Txn Date), with dates read once per file and a list of each column decision.

What it does

Left, inner and full joins of two CSV/Excel files, or two sheets of one workbook
Key auto-detection with a plain explanation; choose your own or a composite key
Key clean-ups counted one by one: spaces, case, leading zeros, Excel number formats, separators, look-alike characters
Unmatched rows on both sides with a likely reason and the closest key; duplicate keys and row fan-out counted
Stack up to 24 files: columns aligned by identical name, then same-name spelling, then a synonym table, then fuzzy matches you confirm
Day/month order decided once per file, EU number formats, total rows and repeated headers removed and listed

Try asking

“Merge orders.csv with customers.xlsx on customer ID and tell me why some orders don't match”

“Combine these 12 monthly exports into one sheet; the column names changed during the year”

“VLOOKUP these two spreadsheets: some IDs have leading zeros and some don't”

Limitations

CSV, TSV and .xlsx only (save older .xls files as .xlsx)
Up to 100,000 rows per side for joins and 200,000 rows in total when stacking
Up to 24 files per stack; formulas are read as their last saved values

Add it

ChatGPT: once Keyjoin Spreadsheet Merge is approved, add it from the ChatGPT plugin directory.

Claude: go to Customize > Connectors > Add custom connector and enter https://sheet-join.zovo.one/mcp. No sign-in is needed. Once Keyjoin Spreadsheet Merge is listed in the Claude connector directory, you can add it from there too.

Other MCP clients can connect to the same endpoint: https://sheet-join.zovo.one/mcp