Guide · Large files
Open a large CSV file without uploading it
Excel spins forever, Notepad freezes, the online spreadsheet rejects the file: past a few hundred MB, a CSV gets hard to open with everyday tools. Here is why, and how to see what's inside, count it and extract the part you need without installing anything.
In short
Don't load the whole file at once: stream it. CSV Géant shows the first 100 rows right away, counts every row, then filters, deduplicates and exports the result in a format Excel opens. The file is read by your browser and sent nowhere.
Why the file won't open
- Spreadsheets have a row cap. An Excel worksheet stops at 1,048,576 rows (Microsoft, “Excel specifications and limits”): the rest is not loaded. See CSV too large for Excel.
- Text editors often load everything into memory and lay out every line for display: a few GB of text is enough to slow them down badly or freeze them.
- Online tools ask you to upload the file, with a size cap, a wait, and your data (customers, accounting) going to someone else's server.
How CSV Géant reads a large file
The browser reads the file in 8 MB chunks, decodes and parses them as they come, in a separate thread (a Web Worker) that doesn't block the page. To count, filter or split, it never needs the whole file in memory.
| Measured on a 2.22 GB file (22 million rows) | Time |
|---|---|
| Preview: encoding and delimiter detection, first 100 rows | 0.3 s |
| Exact row count | 17.4 s and 17.8 s |
| Filter “country = FR” and deduplicate, single download (8,001,769 rows, 0.82 GB) | 71.8 s and 72.0 s |
Conditions: AMD Ryzen 5 4500U, 16 GB RAM, NVMe SSD, Windows 11, Chrome 154 driven by an automated test, two runs per operation. Timings depend on your machine.
Step by step
- Open the tool in Chrome or Edge, on a computer.
- Choose the file or drop it on the drop zone (.csv, .tsv, .txt; multi-GB files welcome).
- Read the preview: column names, first 100 rows, detected encoding and delimiter. Fix them in the lists if characters or columns look wrong.
- Click “Count all rows” to learn the real size of the file and spot rows that don't have the expected number of columns.
- Extract what you need under “Prepare the export”: filter conditions (contains, equals, starts with, number > or <, is empty…), duplicate removal, sorting, columns to keep.
- Export: a single file if the result is small, or several split files if it is still large. The output (UTF-8 with BOM) opens directly in Excel.
What the tool is not
CSV Géant is not a viewer where you scroll through 22 million rows: the preview shows the first 100. To see other rows, filter (for example “name contains Smith”) and export the result, then open that smaller file in Excel. Sorting also applies to the exported file, not to the preview.
Free or Pro
- Free: preview, detection and row count with no size limit. Exports (filter, deduplicate, sort, split) up to 100,000 rows per operation; the tool tells you how many rows the full result would contain.
- Pro, €29 paid once: unlimited exported rows, in the browser where you enter the key. No subscription.
Limits, honestly
- Tested in Chrome only. Edge uses the same engine but is not tested; Firefox and Safari are not tested.
- Largest file measured: 2.22 GB. The streaming read has no size-dependent state beyond that, but it has not been measured.
- Memory: deduplication keeps 16 to 32 bytes per distinct value (about 256 MB for 10 million); sorting keeps the whole result in memory, 3 million rows or 600 million characters at most.
- Download: the output file is first assembled by the browser; above 1 GB of output, choose “Write directly to a folder” (Chrome, Edge).
- One CPU core is used for parsing.
- A single record over 16 MB (usually an unclosed quote) stops processing with a message.
Frequently asked questions
Is my file uploaded to a server?
No. It is read by your browser, on your computer. Once the page has loaded you can disconnect from the internet: the tool keeps working.
What is the maximum file size?
The largest file tested is 2.22 GB (22 million rows). Counting, filtering and splitting read in chunks and don't depend on file size; deduplication and sorting use memory (see the limits).
Can I open a large CSV in Google Sheets instead?
Google Sheets also caps how much data a spreadsheet can hold, and the file has to be uploaded first. If you only need part of the data, filter it here and import the smaller file.
Does it work on a phone or a Mac?
Not tested. The tool is designed for a computer running Chrome or Edge; it has only been measured on Windows.
Finally see what's in your file
Free preview and row count, no size limit.