What Is a .rewind File? The Format, What's Inside, and How to Open One
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A .rewind file is a recording of a spreadsheet editing session, not a spreadsheet itself. It is a ZIP archive of deflate-compressed, MessagePack-encoded components holding a timeline of cell-change events, text notes, and session metadata, with a SHA-256 integrity hash checked on every entry. ExcelRewind, an Excel add-in and Google Sheets add-on, writes it as a companion file next to the original workbook and never modifies that workbook.
What is a .rewind file?
A .rewind file is the output of an ExcelRewind recording session. While you work in Excel or Google Sheets, the add-in captures each cell edit, its timing, and any note you attach explaining why it happened. When you stop recording, that log is packaged into a single .rewind file saved next to the workbook. Opening the file later replays the session edit by edit; it does not open as a spreadsheet in Excel, because it is not one.
| File extension | .rewind |
|---|---|
| Category | Spreadsheet session recording (companion file, not a spreadsheet format) |
| Container format | ZIP archive |
| Entry encoding | MessagePack, deflate-compressed (media entries are stored as-is) |
| Created by | ExcelRewind Excel add-in, ExcelRewind Google Sheets add-on |
| Opened by | ExcelRewind web viewer (browser, no install), ExcelRewind Excel add-in (in-Excel replay) |
| Current format version | 1 |
What's inside a .rewind file?
Under the hood, a .rewind file is a ZIP archive with a fixed set of named entries. Three are always present; the rest appear only when the session recorded that kind of data.
| Component | Entry name | Holds | Present |
|---|---|---|---|
| Metadata | meta.bin | Format version, session title, workbook name, platform, tags, event and annotation counts, per-entry SHA-256 hashes | Always |
| Timeline | timeline.bin | Timestamped cell-change events: sheet, cell address, old and new value, old and new formula, and change type | Always |
| Annotations | annotations.bin | Text notes with a timestamp and an optional cell anchor | Always |
| Audio | audio.webm | Voice narration recorded alongside the edits | Only on audio-tier sessions |
| Video | video.webm | Webcam recording synced to the timeline | Only when webcam recording was on |
| Workbook snapshot | workbook.xlsx | A copy of the workbook as it stood at the end of the session | Optional |
| Object images | media/*.png | Rendered images of charts present at end of session (charts aren't diffable cell data) | Optional |
This is a companion file. Nothing in this archive is the spreadsheet; it is a record of the edits that produced one. With end-to-end encryption enabled, every entry above is sealed with AES-256-GCM under a key wrapped to a passphrase you choose, and entry names stay readable while entry contents do not open without that passphrase.
How do I open a .rewind file?
Two ways, neither requiring the original workbook:
- Web viewer, no install. Go to the free ExcelRewind viewer and drag the .rewind file in. It replays in your browser: a timeline scrubber steps through each cell edit in order, alongside any notes attached to it. No account is needed to view a shared recording.
- In-Excel replay. With the ExcelRewind add-in installed, open a .rewind file from the task pane and it replays on a temporary sheet inside Excel, leaving your live workbook untouched.
Can I convert a .rewind file to Excel?
No, and there is no .rewind-to-xlsx converter. A .rewind file is a recording of edits, not a spreadsheet encoded in a different container. If you need the actual data, you already have it: it lives in the original .xlsx workbook that was open during recording. The .rewind file's job is to show how that workbook arrived at its current state, one edit at a time, not to stand in for it.
Is it safe to open a .rewind file?
Opening a .rewind file in the web viewer runs entirely in your browser; the file is read locally and is not uploaded to replay it. Every entry inside the archive carries a SHA-256 hash recorded in its metadata, and that hash is checked when the file loads, so a corrupted or altered file fails with a clear error rather than silently showing wrong data. With end-to-end encryption enabled, opening also requires the sender's passphrase, and ExcelRewind has no way to read the contents without it. See how encryption works and how data is handled.
Who creates .rewind files?
ExcelRewind is an Excel add-in (with a Google Sheets add-on) that records why the numbers in a spreadsheet change. It captures every cell edit with timing and a note explaining the reasoning, and saves them to a shareable, replayable .rewind companion file. It never modifies the original workbook and never uploads spreadsheet content1.
The ExcelRewind Excel add-in and its Google Sheets add-on. Both record cell edits locally while you work and write a .rewind file when you stop recording. Compare that to what Excel's own tools log in Show Changes and Version History, or see the workflow in practice for financial models.
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Watch a live replayInstall the add-in or see how ExcelRewind records the why behind every number.
Frequently asked questions
What is a .rewind file?
A .rewind file is a recording of a spreadsheet editing session, saved by ExcelRewind. It is a ZIP archive of deflate-compressed, MessagePack-encoded components holding a timeline of cell-change events, text notes, and session metadata with a SHA-256 integrity hash for every entry. It is a companion file: it travels next to the original workbook and never modifies it.
How do I open a .rewind file?
Drag it into the free web viewer at viewer.excelrewind.com. It opens in your browser, no install and no account required, and replays the recorded edits in order. If you have the ExcelRewind add-in installed in Excel, you can also open a .rewind file from inside Excel and replay it on a temporary sheet without touching your live workbook.
Can I convert a .rewind file to an Excel spreadsheet?
No, and there is no .rewind-to-xlsx converter. A .rewind file is a recording of the edits that produced a workbook, not the workbook itself. If you need the actual spreadsheet, use the original .xlsx file; the .rewind file is there to show, edit by edit, how it got that way.
Is it safe to open a .rewind file from someone else?
Yes. Opening one in the web viewer replays it locally in your browser; the file is not uploaded anywhere to be viewed. Every component inside the archive carries a SHA-256 hash that is checked when the file is read, so a corrupted or tampered file fails to open with a clear error instead of showing altered data. With end-to-end encryption enabled, the contents are also locked with AES-256-GCM and need the sender's passphrase to open.
What program creates .rewind files?
The ExcelRewind Excel add-in and its Google Sheets add-on. Both record cell edits locally as you work and save the session to a .rewind file when you stop recording. No other product currently writes this format.
1 The one exception: a Kiosk/Exam mode submission uploads the finished exam recording to ExcelRewind's storage for instructor review, sealed to the organization's encryption key when one is enabled.
Last updated: July 2026.
ExcelRewind is an independent product and is not affiliated with, endorsed by, or sponsored by Microsoft Corporation. Microsoft and Excel are trademarks of the Microsoft group of companies. Questions? [email protected].