How to open a large CSV file on Mac
A bank export, an order history, a pipeline output: the file opens fine until it doesn't, and a spreadsheet gives no warning before it happens. Here's why, and how to open it anyway.
Why a big CSV breaks a spreadsheet
A CSV file has no row limit of its own; it's a text file. What breaks is the spreadsheet reading it. An Excel worksheet holds 1,048,576 rows and 16,384 columns, so a file with more rows than that simply loses everything past row 1,048,576 (Microsoft). A Numbers table stops even sooner, at 1,000,000 rows (Apple). Under that line, both still have to read the whole file into memory before you see the first row, so a few hundred megabytes can mean a long wait, or a spinning beachball, before you find out whether it opened at all.
Open the file in Tabulay
Tabulay is a CSV workbench for Mac built around files that arrive with millions of rows.
- File ▸ Open (⌘O) for a file you trust, or File ▸ Open with Options (⇧⌘O) for one you don't yet.
- Open with Options shows what Tabulay detected: delimiter, encoding (UTF-8 or Windows-1252), header row, decimal separator and date format, each with a live preview, before a single row is opened. Useful for a bank export written with semicolons and decimal commas, or an old file in a legacy encoding.
- Confirm, and the grid opens. Scroll to row 900,000 the way you'd scroll to row 9.
Why it stays fast on a big file
Tabulay doesn't load the file into memory the way a spreadsheet does. It memory-maps it and indexes it in one pass, noting where every row starts; after that, a row is parsed only when it's actually shown or queried. On a 207 MB, 1.3-million-row CSV file, that indexing pass takes 0.35 s, and the first rows appear in 0.2 ms once it's done.1 A bigger file takes longer to index, in proportion; there's no shortcut around reading every byte.
The limit, stated plainly
Files up to 2 GB open for editing in Tabulay. That covers the great majority of CSV exports, millions of rows for most schemas. Past 2 GB, the file still opens, but read-only, so you can look through it, filter it and query it safely without the risk of half-writing it back. There's no free tier and no paid tier for this: it's the same limit either way.
Other ways to open a big CSV
The command line handles a huge file without loading it either: head, less or awk can page through it a chunk at a time or pull out matching lines. That's a fair way to peek at a file or grep for a value, but you're reading text, not working with typed columns, sortable headers or a change you can undo. A spreadsheet stays the right tool for what it's good at: typing data in, building a formula, drawing a chart, for the rows that fit under its limit. Past that limit, or once you need to edit the file itself and keep the rest of it untouched, something built to index the file rather than load it into a fixed grid is the more direct route.
Try it
Open your largest export with File ▸ Open with Options and see what Tabulay detects before it opens a row. The full list of formats, encodings and measured figures is on the tech specs page. For the fuller case against opening a big file in a spreadsheet at all, see Tabulay vs. spreadsheets.
1. Measured on a 207 MB, 1.3-million-row CSV file with a release build of Tabulay's core engine, September 2026. Actual times vary with the file and the Mac.