How to Open Large CSV Files Free (Without Excel or Uploading)

Open the free CSV viewer, drop the file in, and it loads into a DuckDB table called data that you can query with real SQL — joins, aggregates, window functions. The engine and the file both stay inside your browser tab, so a file far larger than Excel can open still works and nothing is uploaded.

Available free in the United Kingdom, United States, Ireland, Canada, Australia and across the EU. Because files are processed in your own browser and never uploaded, no personal data crosses a border, which keeps use consistent with UK GDPR, EU GDPR and CCPA/CPRA expectations.

Frequently asked questions

How large a CSV can this open?

Far beyond Excel's 1,048,576-row limit. The practical ceiling is your browser tab's memory rather than a fixed number, so closing other tabs helps with very large files.

Do I need to know SQL?

For browsing, no. For anything analytical, a single SELECT with GROUP BY answers most questions, and the examples above can be copied and edited.

Is the file uploaded anywhere?

No. DuckDB runs as WebAssembly inside your browser and reads the file from your disk. Nothing is transmitted, which is why it works offline once the page has loaded.

Why did my leading zeros disappear?

Column types are inferred, so an ID column of digits may be read as a number. Cast it to text with CAST(column AS VARCHAR) to preserve the original formatting.