Redaction guides

Excel, XLS, and spreadsheet redaction explained

People search for spreadsheet redaction under half a dozen different names—Excel redaction, XLS redaction, XLSX redaction, workbook redaction, ODS redaction, or CSV masking—depending on which software generated the file. Whatever the file extension, the goal is the same: removing personal names, emails, salaries, tax IDs, and account numbers from rows and columns without breaking the rest of the table or leaving hidden copies behind.

Spreadsheet file formats at a glance

How a spreadsheet stores your data under the hood determines how it must be redacted:

• XLSX (.xlsx) — Modern Microsoft Excel workbook: Introduced in Excel 2007, an .xlsx file is a compressed ZIP archive of XML parts. Cell strings, styles, formulas, charts, pivot caches, comments, and author records each live in separate XML files inside the archive. Our online Excel redaction tool edits .xlsx workbooks directly in place.
• XLS (.xls) — Legacy Excel 97–2003 binary workbook: Older .xls files use Microsoft’s proprietary BIFF8 binary stream format, which can retain deleted strings and unallocated sector slack inside the binary container. To perform clean XLS redaction, open the file in Excel, LibreOffice Calc, or Google Sheets, choose Save As → Excel Workbook (.xlsx), and then redact the .xlsx file.
• ODS (.ods) — OpenDocument Spreadsheet: Used by LibreOffice Calc, OpenOffice, and Collabora, .ods workbooks are also ZIP archives containing content.xml, styles.xml, and meta.xml. AnyRedact opens and exports .ods files natively alongside .xlsx.
• Google Sheets & Apple Numbers: Cloud and Mac spreadsheets don’t circulate as standalone files until exported. In Google Sheets, choose File → Download → Microsoft Excel (.xlsx) (or .ods); in Apple Numbers, choose File → Export To → Excel, then upload the exported workbook to redact it.
• CSV & TSV (.csv, .tsv) — Delimited text tables: Plain comma- or tab-separated files have no hidden worksheets, formulas, or XML caches—just raw lines of text. Open them in our text & CSV redaction tool (or drop them into the Excel tool) to mask values while keeping every delimiter, quote, and column aligned.
• XLSM & XLSB (.xlsm, .xlsb): Macro-enabled and binary workbooks can carry embedded VBA code and binary caches. Save a copy as a standard .xlsx workbook first so macros are stripped and every XML part can be inspected and scrubbed.

Why DIY "redaction" in Excel almost always leaks data

Unlike a flattened PDF image, an Excel workbook is a live database. The most common manual cover-up techniques leave the original data intact for anyone who opens the file:

• Coloring cells black on black: Setting a cell’s fill color to black and font color to black only changes visual styling in xl/styles.xml. Anyone can select the cell to read its value in the formula bar, copy and paste the sheet into Notepad, or change the font color back.
• Hiding rows, columns, or worksheet tabs: Hidden columns and sheets (even sheets set to xlSheetVeryHidden in VBA) remain stored in full inside xl/worksheets/sheet*.xml and can be unhidden in seconds.
• Deleting a column referenced by formulas: If column C concatenates or looks up values from columns A and B, clearing A and B can either break the sheet with #REF! errors or leave cached results sitting inside the formula cells’ <v> tags.
• Forgetting the shared string table: Excel deduplicates text across the workbook in xl/sharedStrings.xml. Poorly written scripts that edit cells without updating shared strings or calculation chains either corrupt the file or leave unreferenced strings behind.
• Leaving PivotTable and chart caches untouched: Pivot tables (xl/pivotCache/) and charts (xl/charts/) save their own snapshot of source rows inside the workbook. Even if you delete the source worksheet completely, a recipient can double-click a pivot cell or inspect the chart data to recover the original records.

What proper Excel and spreadsheet redaction cleans

When you open an .xlsx or .ods workbook in our spreadsheet redaction tool, every layer of the file is handled together:

1. Formatted numbers and dates are read as displayed: Excel stores dates and custom-formatted numbers as raw serial integers (for example, 33970 instead of 01/02/1993). AnyRedact applies the workbook’s number formats before scanning so birth dates, formatted phone numbers, and ID numbers are detected accurately.
2. Row-aware AI + pattern detection: Cells in each row are analyzed together so the AI sees column context—connecting a person’s name in column A with their email, phone number, IBAN, or notes in adjacent columns.
3. Safe formula conversion: Untouched formulas continue to calculate normally. Any formula cell whose value is redacted is automatically converted to a plain inline string (and stale calculation chains are dropped) so Excel never recalculates the secret value.
4. Shared strings, charts, and PivotTable caches updated: Shared string entries are cleanly split or overwritten in place, phonetic furigana guides (<rPh>) are removed, and cached values inside charts and PivotTables are scrubbed to match your redactions.
5. Hidden sheets, comments, and headers included: Hidden and very-hidden sheets are surfaced in the editor tabs, cell notes and threaded comments are scanned (with comment author names replaced by Redacted), and print headers and footers are checked automatically.
6. Metadata and local file paths stripped: Author names, company properties, xl/persons/person.xml contributor IDs, preview thumbnails, and local save-directory paths (absPath) are removed when you download.

Step-by-step workflow for any spreadsheet

1. Convert legacy formats if needed: If your file is an older .xls, .xlsm, or Apple Numbers file, save it as .xlsx first. For .xlsx, .ods, or .csv, open it directly in the Excel & spreadsheet redaction tool.
2. Click Upload to scan: Review detected names, emails, phone numbers, IDs, and payment details highlighted right inside the spreadsheet grid.
3. Toggle or add redactions: Click any highlight in the grid to keep it, select a cell to redact parts of its text in the cell bar, or list internal project names and client IDs under Always redact.
4. Choose your style and download: Export with solid █ blocks or readable placeholders like [NAME] and [EMAIL], then open the downloaded workbook in Excel or LibreOffice to continue working.

For a walkthrough of the grid controls, see how to redact an Excel spreadsheet.