Keyjoin Spreadsheet Merge

Use this when the user wants to merge, match or VLOOKUP two spreadsheets on a shared ID column: "vlookup two spreadsheets", "merge two excel files by customer ID", "match orders to customers", "why are some rows not matching", "find which IDs are missing from the other file". Attach both files (CSV, TSV or .xlsx; or one workbook with two sheets) or paste both tables. Left join by default (all left rows kept); inner and full joins are available. Auto-detects the key column and explains why (override with left_key/right_key, or give a composite key). Key clean-ups are applied in order and each is counted: spaces, case, look-alike characters, Excel number formats (12345.0, 1.2345E+05), separators, leading zeros (C00123 = C123), letter prefix used by one file only; turn any off with skip_normalizations. Reports unmatched rows on both sides with a likely reason and closest key, duplicate keys with fan-out counts, and returns an Excel workbook (Merged, Unmatched left, Unmatched right, Duplicates, Summary) plus a merged CSV. Does not do mail merge (letters, labels, emails), does not compare two versions of one file cell by cell, and does not edit the original files.

Use this when the user wants to stack or append many spreadsheets into one: "combine multiple csv files into one", "merge 12 monthly excel files", "combine excel files with different column names", "append these exports into one sheet", "combine all sheets into one". Takes 1 to 24 CSV, TSV or .xlsx files (or pasted tables). Aligns columns by identical name, then same name with different case or spacing, then a synonym table (Amt = Amount, Txn Date = Date, Memo = Description), then fuzzy spelling matches that are listed for confirmation; a specific column is not folded into a more general one (Spouse First Name stays separate from First Name). Adds a Source file column, decides day/month order once per file, reads EU number formats, removes total rows and repeated headers (listed), and reports each column decision. Returns an Excel workbook (Combined, Column mapping, Files, Excluded rows, Summary) and a CSV. Does not join files side by side on an ID (use join_spreadsheets) and does not do mail merge.