Common questions

Why is my Excel file so large?

An .xlsx is a ZIP holding XML, images and other parts, so its size is the sum of those parts. The usual culprits are the worksheet data itself, pivot caches, embedded images, and formatting applied thousands of rows past the last real one. This tool lists every part and what it costs, so you can see which one is responsible instead of guessing.

Does shrinking change my formulas, values or formatting?

Not the ones on by default that touch nothing visible. They remove the formula calculation cache, which Excel rebuilds the next time the file opens, and empty cells that show nothing their row or column would not show anyway. A column formatted cell by cell down to the last row gets one column format instead, and conditional formatting that Excel split into hundreds of pieces is joined back into one rule where that cannot change what any cell shows. Every value, formula, visible format, image, chart and name is untouched. Turn it off and only the ZIP packing changes, which makes the contents byte for byte identical. The copy is compared against the original before you are offered a download.

How much smaller will my file get?

It depends entirely on what is inside. Across the sixteen real workbooks measured on the measured-files page, the default set took 47.6% off the total, and the individual results ran from nothing at all to 99.9%. Repacking alone, with every reduction switched off, accounted for 6.5% of that total. Rather than promise a percentage, the tool reports what it actually saved, itemises what it removed, and tells you what any reduction you switched off would have recovered.

Is my spreadsheet uploaded to a server?

No. There is no upload and no server involved in processing. The page is static files and the work runs in WebAssembly inside your browser tab. You can confirm it by opening the Network tab in your developer tools while you shrink a file, or by disconnecting from the internet and shrinking one anyway.

Does it work with .xls, .xlsm or .xlsb files?

Macro-enabled .xlsm workbooks and .xltx or .xltm templates work; the macros pass through untouched. Legacy .xls and binary .xlsb are different formats and are refused with a reason, as are encrypted and digitally signed packages. Open an .xls in Excel and save it as .xlsx first.

Will a smaller file open or calculate faster in Excel?

Not necessarily, and the tool does not claim it. Recompression changes how the file is packed on disk, not how much work Excel does once it is open, and removing the calculation cache can cost a little time on the first open while Excel rebuilds it. What a smaller file reliably helps with is storage, email attachment limits and sync time.

How large a workbook can it handle?

Up to 100 MB on disk, and the size on disk is not really the question. A workbook is a zip, and its XML unpacks ten times over or more, so a 30 MB file can hold 600 MB of data and that is what has to fit in the tab alongside your file, a working copy and the result. Past our own budget the page asks your browser for the room before refusing, so a machine with memory to spare runs a workbook a smaller one cannot. Files over about 40 MB will be slower, and the page says so before it starts.

Does the desktop app have the same limits?

It has limits, and they are not the browser ones. Nothing about a workbook sets them: they are budgets we choose so a bad file cannot exhaust the machine. A browser tab is the tight case, because 32-bit WebAssembly addresses 4 GB at most and the tab dies rather than refusing, which is why the page is careful. A desktop process has real memory and can say no politely, so the app takes a workbook up to 512 MB on disk and 2 GB unpacked, and refuses one past that with a reason instead of falling over.

What does the site record when I shrink a file?

Numbers, twice. Before a run: the size of the file, how much it says it holds unpacked, and the extension. When it finishes: the size after, how long it took, which reductions ran, what the ones you left off would have recovered, and where the space was. No file name, no sheet or part name, no account, no cookie. The first line exists because a workbook large enough to exhaust a tab can take the page down with it, and a run that never comes back is the one thing we cannot otherwise learn from. It is sent as a plain link you can read in the Network tab, and the privacy page lists the whole of it.

What are the reductions, and which are safe?

Every one of them runs. Most take back things nothing can miss: the calculation cache, which Excel regenerates, fragmented conditional formatting rejoined, cells holding only an empty string, which Excel drops on save anyway, empty invisible shapes in workbooks without macros, and empty cells that look identical to no cell at all. One changes a visible thing you can put back in a click, a fill or border on empty rows past your data. One changes how the file behaves on opening: pivot source copies Excel can rebuild from this workbook go, so the pivot refreshes on open. And three remove content outright: defined names whose target is gone, cached values from linked workbooks, and the Power Pivot data model. Your original is never touched, so anything you did not want removed is still in the file you started with.

Do I need to install anything or create an account?

No. There is no install, no sign-up, no email and no watermark. Open the page and drop a file on it. The desktop app is the paid one: it takes whole folders, runs the same engine on every workbook across every core, and writes copies into a folder you choose so every original stays where it is.

The numbers above come from sixteen measured workbooks. Drop your own file to see what it says about yours.