How they compare
| Feature | LibreOffice Calc | Viztab |
|---|---|---|
| Row limit | 1,048,576 rows | 10,000,000+ rows |
| Column limit | 1,024 columns | No fixed limit |
| File size handling | Freezes on 200 MB+ files | 2 GB+ tested |
| Startup time | 3-10 seconds (heavy desktop app) | Instant (browser tab) |
| Install required | Yes — 300+ MB download | No — runs in browser |
| Data privacy | Local processing | Local processing |
| Formulas | 500+ functions | 370+ functions |
| Macros | Basic, Python, JavaScript | Not supported |
| Price | Free & open source | Free tier + Pro for large files |
| Platform | Windows, macOS, Linux | Any browser + desktop app |
Same row limit as Excel
LibreOffice Calc uses the same XLSX-compatible format as Excel and inherits the same 1,048,576-row limit. When you open a CSV with more than a million rows, LibreOffice Calc will truncate it silently, loading only the first million rows and discarding the rest.
In practice, LibreOffice Calc starts struggling well before that limit. Files with 200,000+ rows can take a long time to open, and scrolling through large datasets is noticeably slow compared to dedicated data tools. Memory usage climbs rapidly with file size.
Viztab has no imposed row limit. Its streaming engine handles 10 million+ rows, and loading is progressive — you see the first rows immediately while the rest indexes in the background.
Lightweight vs. heavyweight
LibreOffice is a full office suite that includes a word processor, presentation tool, drawing app, database, and more. A typical installation is 300-500 MB, and the application takes several seconds to start up. On older hardware, LibreOffice Calc can feel sluggish even with small files.
Viztab is a single-purpose tool focused entirely on spreadsheet performance. It runs in a browser tab with no installation. You can be viewing your data in seconds rather than waiting for an application to boot. The desktop app, if you prefer it, is under 15 MB.
Cross-platform without compromise
LibreOffice runs on Windows, macOS, and Linux, but the experience varies across platforms. The macOS version in particular has historically had interface quirks and rendering differences. Each platform requires a separate download and installation.
Viztab works identically in any modern browser — Chrome, Firefox, Safari, Edge — on any operating system. There is nothing to install and no platform-specific differences. You get the same experience on a Chromebook as on a high-end desktop.
When LibreOffice Calc is the better choice
LibreOffice Calc is an excellent general-purpose spreadsheet application. It is free, open source, and supports macros in multiple languages (Basic, Python, JavaScript). If you need a full-featured spreadsheet that works offline and handles complex formatting, conditional formatting, charts, and pivot tables, LibreOffice Calc is a strong option — especially for users who want a free Excel alternative.
But when your primary challenge is working with large datasets that exceed the 1-million-row limit, or when you want something lighter and faster to open big CSVs, Viztab is the right tool for the job.
Frequently asked questions
Yes. Viztab opens XLSX files natively, which is the most common format used by LibreOffice Calc for Excel-compatible files. You can also save LibreOffice Calc files as CSV and open them in Viztab for the best large-file performance.
No. LibreOffice Calc has the same 1,048,576-row limit as Excel when working with XLSX files. Its native ODS format technically allows more rows, but in practice, performance degrades severely with large datasets well before reaching any theoretical limit.
Viztab uses a streaming architecture that indexes data progressively rather than loading everything into memory at once. It only renders the rows visible on screen, which means scrolling through 10 million rows is as fast as scrolling through 100. Traditional desktop spreadsheets load the entire file into memory before displaying anything.
Viztab currently supports CSV, TSV, and XLSX formats. If you have an ODS file, you can convert it to CSV or XLSX using LibreOffice Calc (File > Save As) and then open it in Viztab.
Handle large files without the bloat
Skip the heavy desktop app. Viztab opens your big spreadsheets instantly, right in your browser.
Open Viztab