Synthetic examples: reuse-a.csv reuse-b.csv
LOCAL SPREADSHEET TOOLS
Merge Excel and CSV files without mixing up columns
Append local tables using explicit UNION or INTERSECTION schemas, preserve source rows, and review conflicts before exporting an auditable workbook.
When appending rows is the right task
Combine monthly exports or regional lists that describe the same kind of record. This tool appends rows; it does not compare versions, deduplicate records, or match related records horizontally. Use Lookup for a key-based join and Compare to inspect changes.
How it works
Choose two or more local XLSX or UTF-8 CSV inputs, adding input slots as needed. Each input selects one sheet and confirms its header row. Selecting the same workbook again can select another sheet. Header suggestions are not applied automatically. Choose comma, semicolon or tab explicitly for CSV.
UNION keeps every column identity and fills absent values with blank cells. INTERSECTION retains identities shared by every included input and lists excluded schema fields in the audit. Column order does not decide identity. Unique exact titles match; duplicate, empty or no-header columns need explicit identities. You can give differently named columns the same identity intentionally.
Synthetic example
Input 1 has ID, Value with row 00123, Alpha. Input 2 has Value, ID, Extra with row Beta, 00123, New. UNION produces ID, Value, Extra and correctly aligns 00123 with Beta despite reversed columns. INTERSECTION keeps ID and Value. All example files below are synthetic.
Data includes Input N, selected sheet and original one-based row. Original filenames and local paths are not written to exports. Same identity with text in one source and numbers in another generates a warning; no conversion repairs the difference.
Privacy and safe output
Files and results remain in the local browser Worker. There is no upload endpoint, user-content analytics, advertisement or persistent business-data storage. Clear and Cancel terminate processing and release session references/download URLs.
Export XLSX for Data, Summary, Schema, Inputs and Run_Settings. The report records local generation time and your rules. Date serials/epochs and formula/cache representations become explicit audit text; formulas never run or inherit active content. CSV is a data-only alternative with type-loss and formula-prefix warnings, not the complete audit.
Limits before running
Each workbook has default content budgets of 10,001 cumulative rows and 300,030 rectangular cells, with no fixed original-file size cap. Advanced permits up to 100k × 30 per input, subject to Core ZIP/XML/text gates. The session accepts at most 8 inputs and two effective input budgets of retained cells, model text and XLSX expanded content. Mobile/low-memory limits are lower.
Outputs must fit 256 columns including lineage, the Excel row bound and the 650k default / 6.5m advanced cell budget including audits. Wide or large results block; they are never silently truncated or split. Multiple retained files and XLSX output can consume substantial memory. Desktop recommended; 100k is experimental and there is no 16 GiB or physical Safari guarantee.
Frequently asked questions
Does an empty sheet disappear? No. It blocks until you explicitly choose to skip that input; the skip and sheet remain in the audit. If all inputs are skipped, there is no valid merge.
Does UNION guess that Order ID and ID mean the same thing? No. Give both the same explicit identity if you have verified that meaning. Blank strings and blank cells remain distinct when the source format preserves them; CSV quoted-empty provenance remains unknown.
Can I merge every workbook? No. XLS/XLSM, macros, external links and unsupported or over-budget structures are rejected. The guide describes the supported data workflow, not complete Excel-format compatibility.