Protection

Passwords are informational

Worksheet and workbook protection are not file encryption. A protection password tells applications to ask for it. Nothing stops a program from ignoring it.

Mark as final

const XLSX = require("@agent-sheet/wasm");
const wb = XLSX.utils.book_new();
XLSX.utils.book_append_sheet(wb, XLSX.utils.aoa_to_sheet([[1]]), "S");
wb.Custprops = { _MarkAsFinal: true };
const back = XLSX.read(XLSX.write(wb, { type: "buffer", bookType: "xlsx" }));
console.log(!!(back.Custprops && back.Custprops._MarkAsFinal));

Output

true

Workbook structure protection

wb.Workbook.Protection = { lockStructure: true, lockWindows: false } stops users from adding, moving, hiding and renaming sheets (lockStructure). It also fixes the window size and position (lockWindows). The XLSX reader and writer support these flags. A password property on this workbook object is not written; worksheet passwords are separate. Use template editing when you also need to preserve unrelated file content.

Worksheet protection

ws["!protect"] turns on sheet protection. An empty object protects the sheet with the defaults below. Each key is one permission. The value is inverted: true means the action is disabled (locked), and false means it is enabled (allowed). This matches the sheetProtection attributes in the file.

Key	Permission	Default when protected
selectLockedCells, selectUnlockedCells	select cells	enabled
formatCells, formatColumns, formatRows	format	disabled
insertColumns, insertRows, insertHyperlinks	insert	disabled
deleteColumns, deleteRows	delete	disabled
sort, autoFilter, pivotTables	sort, filter, use PivotTables	disabled
objects, scenarios	edit objects and scenarios	enabled

const XLSX = require("@agent-sheet/wasm");
const ws = XLSX.utils.aoa_to_sheet([[1, 2]]);
ws["!protect"] = { formatCells: false, selectLockedCells: true };   // allow formatting, block selecting locked cells
const wb = XLSX.utils.book_new();
XLSX.utils.book_append_sheet(wb, ws, "S");
const p = XLSX.read(XLSX.write(wb, { type: "buffer", bookType: "xlsx" })).Sheets.S["!protect"];
console.log(p.formatCells, p.selectLockedCells, p.insertRows);       // false true true

Output

false true true

The password property can set a sheet password on this path. For an existing template workbook, use utils.template_sheet_set_password. See Template: protection.

Per-cell hidden and editable flags are described in Cell styles.