In Excel: use File ▸ Info ▸ Protect Workbook ▸ Always Open Read-Only for a polite prompt, or Save As ▸ Tools ▸ General Options and set a Password to modify for one that cannot be dismissed.
For a nudge: File ▸ Info ▸ Protect Workbook ▸ Always Open Read-Only, then save.
For enforcement: File ▸ Save As ▸ Browse ▸ Tools (beside Save) ▸ General Options ▸ Password to modify. Record the password — there is no recovery.
To undo either, open the file with edit rights and clear the same setting, then save.
If the file still opens read-only, check the file itself: right-click ▸ Properties ▸ uncheck Read-only on Windows, or Get Info ▸ Sharing & Permissions on macOS.
On a network share or SharePoint, also check that you have write permission and that nobody else has the file open.
What this does
Excel has three different things called "read-only", and they are not equally strong. **Always Open Read-Only** sets a flag in the file: every opener sees a prompt asking whether to open read-only, and anyone can answer no. **Password to modify** (Save As ▸ Tools ▸ General Options) requires a password before edits can be saved — without it you can still open and read, but not overwrite. **Mark as Final** is only a hint; one click on "Edit Anyway" removes it. Separately, the operating system's own read-only file attribute (Finder ▸ Get Info, or the Windows file Properties dialog) blocks saving over the file regardless of what Excel thinks, which is why a workbook can open read-only with none of the Excel settings turned on. The same idea underpins a lot of everyday Excel work, so the few minutes spent getting it right here pay back across every sheet you build afterwards. Treat it as a pattern, not a one-off, and it stops being something you look up and starts being something you reach for. Treat “open excel file read only” as a small repeatable workflow rather than a one-off click you hope to remember next time. Use a small test block before the live file, so any surprise in the affected cells shows up while it is still harmless. When this is a ribbon command, the selection matters more than the button: confirm the range, apply the command, then spot-check the output before saving. That turns a data step that keeps your analysis trustworthy into a method you can reuse, explain, and defend when the workbook leaves your screen.
A worked example
A price list several people consult and one person maintains: File ▸ Info ▸ Protect Workbook ▸ Always Open Read-Only, then Save As ▸ Tools ▸ General Options ▸ Password to modify = the maintainer's password. Colleagues open it, get the read-only prompt, read the prices and cannot overwrite the file; the maintainer types the password and edits normally. Read-only is the right control when a workbook is meant to be consulted by many and maintained by one — but only the modify-password variant actually enforces that. A practical tip before you scale it up: build it once on a small block of test data, confirm the number against the tool on this page, and only then point it at your real sheet. That one habit catches almost every mistake while it is still cheap to fix, long before a wrong figure reaches a report or a colleague.
In Google Sheets
If you are in Google Sheets rather than Excel, the good news is that the formula shown here is identical and the workflow barely changes — menus sit across the top instead of in a ribbon, and a few function names differ slightly, but anything you build here moves across with little or no rework. Nothing on this page is behind a login: the tool runs entirely in your browser, the formula is shown in full with one-click copy, and the steps work the same on Windows and Mac. That is the whole promise here — the exact answer, a way to prove it on your own numbers, and just enough context to make it stick. Here is the takeaway for “open excel file read only”: copy the answer if you are busy, but if you have a spare few minutes, rebuild the example in Excel yourself with the tool above open beside it. That single pass — type it, run it, watch the result move when you change an input — is what turns a formula you found into a technique you trust. Keep your inputs labelled and referenced, never hard-coded, and the same sheet stays correct and auditable as it grows. Done that way, you will not need to look this up again, and you will be the person others ask.
Common mistakes
- Trusting Mark as Final as protection — it is a label, and "Edit Anyway" removes it in one click.
- Confusing "Password to open" with "Password to modify": the first stops people reading the file at all.
- Setting a modify password and losing it — Excel cannot recover it, and the workbook can then only be read.
- Blaming Excel when the read-only flag is on the file or the folder permissions, where no Excel setting will change anything.
- Assuming read-only protects the numbers: anyone can save a copy under a new name and edit that freely.
Frequently asked questions
How do I make an Excel file read-only?
File ▸ Info ▸ Protect Workbook ▸ Always Open Read-Only for a prompt, or Save As ▸ Tools ▸ General Options ▸ Password to modify to enforce it.
How do I remove read-only from an Excel file?
Open it with edit rights and clear the same setting you set, then save. If it was the file attribute, uncheck Read-only in the file's Properties (Windows) or fix permissions in Get Info (macOS).
Why does my Excel file open as read-only when I did not set it?
Usually the file or folder is marked read-only by the operating system, the file is open by someone else on a shared drive, or it came from the internet and is in Protected View.
Is read-only the same as protecting a sheet?
No. Sheet protection locks cells inside a workbook you can still save; read-only governs whether the file itself can be overwritten.