The WebAssembly module is 1.6 - 1.8 MB brotli-compressed depending on the Wasm feature set. We're currently investigating ways to reduce this to around 1 MB. We further use streaming instantiation which means that the WebAssembly module will be compiled while downloading it. But still, it will hurt a bit more than a 40KB library.

Regarding multi-tab usage: Not today. The available filesystem apis make it difficult to implement this right now. We're looking into ways to make DuckDB-Wasm persistent but we can only read in this release.