LK Software
Native Windows app · 100% offline

Open the spreadsheets Excel can't.

Hundreds of megabytes, millions of rows — the exports that freeze Excel open in seconds, right on your PC. A real accounting workbook of 1.36 GB opened in about 10 seconds. Nothing is ever uploaded.

Launching soon · $29 one-time See how it works
Data never leaves your PC Read-only — never edits your file
The wall

Excel gives up at 1,048,576 rows.

Past that it freezes, truncates, or crashes. Cloud viewers can open big files — but they make you upload the data first.

Today
1,048,576

The hard row limit

Your export opens for five minutes, then Excel stops responding. Or a cloud tool asks you to upload financial records you're not allowed to send anywhere.

With FastSheet
~10s

Open it on your own machine

A native desktop app streams the whole file locally — millions of rows, instant column stats, filter, find. Read-only, offline, done.

Why it matters

Your data never leaves this PC.

Finance, accounting and ops teams handle records they're forbidden to upload — customer details, account numbers, year-end figures. FastSheet runs 100% offline. No account, no server, nothing to upload. The file stays exactly where it is.

No network calls · verifiable offline
1.36 GB
real workbook, opened on a laptop
~10s
to open it — Excel wouldn't
100%
offline — never uploaded
.xlsx · .csv
Excel & CSV, read-only
How it works

Three steps. No setup.

Open the file

Drag in a CSV or XLSX — hundreds of megabytes, millions of rows. It loads on your machine in seconds.

Read & explore

Instant column stats (sum, average, min/max), Excel-style filters, find across the whole file, jump to any cell.

Export the view

Save just the filtered rows to a new CSV. Your original file is never touched — FastSheet is read-only by design.

Pricing

Buy it once. Keep it.

One-time license · no subscription
$29 one-time
Pay once. No subscription. Free updates within the version.
Launching soon
The engine is done and fast today Windows 10 & 11 · secure checkout

Checkout opens shortly — we're finishing distribution. The app already runs; this page is honest about where we are.

Questions

Straight answers.

Is my data really private?

Yes. FastSheet is a desktop app that reads the file locally. It makes no network calls — you can verify with any firewall monitor. Nothing is uploaded, ever.

How big a file can it open?

It's built for the files that choke Excel — hundreds of MB, millions of rows. A real 1.36 GB workbook opened in about 10 seconds. It loads the file into memory, so it's tuned for large files, not 50 GB datasets.

Will it change my file?

No. FastSheet is read-only. To keep a subset, it exports a brand-new file — your original is never modified.

When can I buy it?

Soon. The engine is finished and fast today; we're setting up checkout and signing. This page will switch to a buy button the moment it's live — no waitlist games.

Windows only?

Yes, Windows 10 and 11 for now. Mac is on the roadmap if there's demand.

Subscription?

No. One-time price, one-time payment. You keep the app.