Browser SQL Lab lets you upload a CSV, JSON, XLSX, or Parquet file and query it with real SQL, powered by DuckDB compiled to WebAssembly. Your file is processed entirely in your browser and never uploaded to a server. Please enable JavaScript to use it.
No. The SQL engine (DuckDB, compiled to WebAssembly) runs inside this browser tab, and your file's bytes are handed straight to it. You can verify this yourself: open your browser's Network tab, load a file, and run a query — you'll see no network activity related to your data.
CSV, JSON, XLSX (Excel), and Parquet. You can import several files and join or compare them with regular SQL, just like separate tables in a database.
There's no hard cap on file size, but the SQL engine runs as 32-bit WebAssembly in your browser, which caps any single allocation — like the hash table built during a join — at around 2 GiB, regardless of how much RAM your machine has. This mostly only matters for large joins or aggregations, not for browsing or filtering a single file. If you hit it, try selecting fewer columns before joining, filtering each side down first, or pre-aggregating one side before combining.
No — reloading the page gives you a fresh, empty session, same as opening a new in-memory database. Nothing is written to disk, which is part of how it stays private. Re-import your files after a reload to continue where you left off.
DuckDB — a real, full-featured analytical SQL database — compiled to WebAssembly via duckdb-wasm, so it runs at near-native speed directly in the browser.
No installation and no account. Everything runs from this page, and after the first load, the app itself works offline — only your data transfers (i.e. none) happen over the network.