Start by making a duplicate and leaving the original untouched. Then identify the problem: a workbook that will not open needs recovery; questionable results need formula checks; an unfamiliar file needs an inventory; unexplained edits call for a version comparison; and a slow or oversized file needs cautious performance cleanup. Excel’s built-in tools can show you what is in a workbook and where to investigate—but they cannot decide whether its business assumptions are sound.
First, protect the workbook you were handed
Save an untouched original, then diagnose a separate copy. Recovery attempts and cleanup can change or remove content, so keeping the original gives you a way back. If the workbook is stored on a network or a disk that is having problems, Microsoft advises moving it to a local disk before attempting recovery.
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Choose the next step by symptom rather than editing cells at random:
- It will not open or reports corruption: use File Recovery or Open and Repair.
- It opens, but figures look wrong: inspect errors and formula dependencies.
- You do not know what is inside: run Workbook Analysis if your Excel edition includes it.
- You need to know what changed: compare the file with a meaningful earlier version.
- It is unexpectedly slow or large: investigate formatting and calculation load on the copy.
1. Recover a workbook that will not open
If Excel detects a damaged workbook, let File Recovery run. If the file still will not open, try Open and Repair. Microsoft’s recovery guidance is at Repair a corrupted workbook.
- In Excel, select File > Open.
- Select the workbook. Open the dropdown beside the Open button, then choose Open and Repair.
- Choose Repair first. It attempts to recover as much workbook data as possible.
- If Repair does not recover what you need, repeat the process and choose Extract Data to try to recover values and formulas.
Recovery may not restore everything. Microsoft also recommends considering a last saved version or other recovery methods; do not treat a repaired copy as proof that every sheet, formula, or result is intact. Check the recovered file against the original or a known-good version before relying on it.
2. Inventory an unfamiliar workbook with Workbook Analysis
Workbook Analysis, part of Spreadsheet Inquire, can produce a report covering workbook details, formulas, cells, ranges, warnings, and data connections. Microsoft’s examples include hidden sheets, linked workbooks, external connections, array formulas, and formulas with errors. The report gives you places to investigate; it does not certify that the workbook is correct or safe. See Microsoft’s overview of what Inquire can do and its Workbook Analysis instructions.
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Check whether Inquire is available
In Excel for Windows, look for it under File > Options > Add-ins > COM Add-ins. If Inquire is not listed, your Excel or Office edition may not include it, or an administrator may have disabled it. Microsoft says Inquire is available only in Excel for Windows in Microsoft 365 Apps for enterprise and equivalent editions; the Excel web app does not provide these workbook audit and compare features. Confirm current availability in Microsoft’s Inquire availability information.
Read the report as an inspection list
Use the report to locate items that deserve human review: hidden sheets, external links, unusual formulas, or error cells. A hidden sheet may be legitimate; a connection may be expected; an error may be contained or consequential. Workbook Analysis also cannot process a sheet whose used range exceeds 100 million cells, according to Microsoft’s Workbook Analysis documentation.
3. Compare versions to find what changed
If you have a useful baseline—such as a version saved before the handoff—Spreadsheet Compare can show cell-level differences between two open workbooks. It can distinguish changes involving values, formulas, named ranges, formats, and VBA code. Microsoft explains the workflow in Compare workbooks using Spreadsheet Inquire.
- Open both workbook versions in Excel.
- Use the Compare Files command in Spreadsheet Inquire.
- Review the reported differences and identify which ones affect the cells, formulas, or workbook elements relevant to your task.
A comparison identifies differences, not which version is right. Without a meaningful baseline, it cannot establish when a change occurred or whether it was intended. If Inquire is unavailable in your edition, this particular audit-and-compare feature is not available in Excel for the web.
4. Trace questionable results with Formula Auditing
When a workbook opens but a result seems wrong, investigate how the formula is built and what feeds it before changing the formula. Excel’s Formula Auditing tools help trace possible causes; they cannot verify that the underlying assumptions or inputs are appropriate for the business question. Microsoft documents these tools and related error checks in its formula error and auditing guidance.
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- Error Checking: inspect formula errors and warnings that Excel identifies. An error such as
#REF!can indicate a broken reference, but the specific cause needs investigation. - Trace Precedents: display arrows to cells that feed the selected formula.
- Trace Dependents: display arrows to formulas that rely on the selected cell.
- Evaluate Formula: step through parts of a nested formula to see how Excel evaluates its components.
- Watch Window: keep selected cells visible while you inspect other parts of the workbook.
A warning that a formula differs from its neighbors is a clue, not a verdict. The difference may be deliberate—for example, because a row has a different role. Check the formula’s inputs and purpose before copying a neighboring formula or dismissing the warning. Dependency arrows can also help investigate circular references, but identifying a relationship does not by itself tell you whether it is intended.
Independent reader supportYour contribution helps us test, update, and keep practical guides available for everyone.5. Investigate a slow or oversized workbook carefully
A workbook that is unexpectedly large, slow, or unstable may have excessive formatting or heavy calculation work. Microsoft’s guidance on cleaning up a workbook so it uses less memory includes the Clean Excess Cell Formatting feature. Treat cleanup as an experiment: work on a duplicate, remove only a suspected cause, then check whether the file’s behavior changes.
Do not assume that a large file is automatically corrupt or that formatting is the only cause. Calculation load may also matter. If cautious cleanup does not solve the problem, Microsoft lists later options such as using 64-bit Excel, splitting a workbook, or contacting support in its workbook memory guidance.
What Excel’s checks cannot tell you
These tools can expose structure, errors, dependencies, differences, and possible performance problems. None can establish whether the workbook’s business logic is appropriate, whether its assumptions are current, or whether a reported change was authorized. For those questions, you need context from the workbook’s owner or someone responsible for the process it supports. Keep findings separate from conclusions: record what Excel flagged, then verify what the item means before changing the file or relying on its output.
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