Question 1

How big a file can I compare?

Accepted Answer

Depends on your browser memory. On a 16 GB laptop we comfortably handle ~200k rows × 30 columns. A warning banner appears past 100k rows. Over 500k rows we recommend splitting the workbook into 2–3 passes.

Question 2

Are files really not uploaded?

Accepted Answer

Yes. The site is static S3 hosting — there is no upload endpoint to send anything to. Open DevTools → Network, run a compare, and the upload tab stays at zero bytes. After the page first loads you can go offline and it still works.

Question 3

How are merged cells handled?

Accepted Answer

The top-left cell of a merged range is treated as the value for the whole range — the same simplification Excel uses when reading merged cells. So a merged header or summary row is compared by that single top-left value.

Question 4

Can you diff Excel formulas?

Accepted Answer

By default formulas are compared by their computed value. If you need to diff the raw formula text (=SUM(A1:A10) vs =AVERAGE(A1:A10)), convert to values first (Paste Special → Values) and re-upload.

Question 5

Does CSV work?

Accepted Answer

Yes — we auto-detect commas, tabs, semicolons and pipes. UTF-8, UTF-8 with BOM, and CP949 (Korean) encodings are attempted. If Korean characters look garbled, re-save as UTF-8 in Excel first.

Question 6

Can I use multiple key columns?

Accepted Answer

The MVP supports a single key column. For composite keys, add a helper column like =A2&"-"&B2 in Excel and pick that. Native composite-key support is on the roadmap.

Question 7

How do I compare multiple sheets?

Accepted Answer

Pick the sheet on each side separately — the names can differ (e.g. A "2024" vs B "2025"). A workbook-wide diff across all sheets at once is on the roadmap.

Question 8

Does row order matter?

Accepted Answer

No — matching is by key-column value, so rows can be in any order on each side. Duplicate keys fall back to positional pairing within that key group.

Question 9

Are numbers and dates matched across formats?

Accepted Answer

Numbers compare as their underlying double, so 1,000 / 1000 / 1.0e3 are equal. Dates stored as Excel serials compare across different display formats. Dates stored as plain strings (e.g. "2025-03-01") fall back to string comparison.

Question 10

What if columns were added or removed?

Accepted Answer

We union the headers from both files. A-only columns show empty on the B side (and vice versa) and surface as modifications. Identical headers that differ only in whitespace, case, or fullwidth/halfwidth forms are auto-normalised.

Question 11

Can I export only the changes?

Accepted Answer

Yes — the XLSX export has 4 tabs (Summary · Modified · Added · Removed). The Modified tab is a Key / Column / Before / After table that review meetings can use directly. CSV export bundles all three sections into one file.

Question 12

Can the exported XLSX highlight changed cells with color?

Accepted Answer

On-screen the table uses yellow highlights. The current XLSX Modified tab is a plain Key / Column / Before / After table. A full-sheet export with cell-level yellow/green/red fills is planned.

Question 13

Does it work on mobile?

Accepted Answer

Works on iOS Safari 16+ and Android Chrome. Mobile memory/screen constraints make it best suited for small sheets (up to a few thousand rows). Use a desktop for bigger files.

Question 14

My company blocks file uploads. Is this tool safe to use?

Accepted Answer

The site is pure static hosting (S3 + CloudFront) — there is no backend to receive files. Parsing happens in the SheetJS runtime inside the browser. Some enterprises restrict even third-party JS, so check with your security team. An on-prem build is available on request.

Question 15

Do you log or store anything?

Accepted Answer

We use GA4 and Naver Analytics for page-view counts only. No file contents or cell values ever leave your browser — nothing is transmitted to begin with. Only your language preference is stored in localStorage.

자주 묻는 질문