chdb-wasm browser shell

The browser SQL shell behind wasm.chdb.io — chDB (ClickHouse compiled to WebAssembly) running fully in the browser. SQL executes on the client, with no backend.

This repo is just the web page + its Vercel deploy. The engine itself (the WebAssembly build, the glue JS, and the .wasm) lives in the chdb-wasm npm package (built from chdb-io/chdb-core); this shell only consumes it.

Layout

• web/index.html — the shell. It references ./dist/...; the build rewrites ./dist to a content-hashed ./dist-<hash>/ directory so the engine can be cached forever.
• vercel.json — deploy config: COOP/COEP cross-origin-isolation headers (needed by the multi-threaded build), immutable caching for the hashed engine dir, no-cache for the page, plus the build command and output directory.
• scripts/build-vercel.sh — assembles the deploy output (out/) from the installed chdb-wasm engine + web/, content-hashing the engine dir.
• scripts/serve.mjs — local preview server (sets COOP/COEP).

Local preview

npm install                 # pulls the chdb-wasm engine into node_modules/
npm run serve               # http://localhost:8099  (use localhost for SharedArrayBuffer)

index.html loads the engine from ./dist; the preview server maps /dist/* to the installed chdb-wasm package. To preview an unpublished local build instead, symlink it:

mkdir -p node_modules && ln -s /path/to/chdb-core/packages/chdb-wasm node_modules/chdb-wasm

Deploy (Vercel)

Hosted on Vercel as a static site — no backend. Everything, including the ~100 MB .wasm, is served as a same-origin static asset straight from Vercel's CDN; Vercel has no per-file size limit, so there is no external object store or streaming function (unlike the old Cloudflare Pages + R2 setup). Serving the wasm same-origin also satisfies the COOP/COEP cross-origin isolation the multi-threaded build requires.

Deploys use Vercel's Git integration: pushes to main publish production, pull requests get preview URLs. On each build Vercel installs chdb-wasm (a dependency), then runs scripts/build-vercel.sh (the buildCommand in vercel.json) to emit out/.

One-time setup (Vercel dashboard, on the clickhouse team):

• Import this repo. Framework preset Other; the build command and output directory are read from vercel.json (bash scripts/build-vercel.sh → out/).
• Add the custom domain wasm.chdb.io and point its DNS at Vercel.
• Plan: only the multi-threaded (mt) engine ships (~95 MB) — the page is always cross-origin isolated, so the single-threaded fallback is never used. That fits Vercel's static-upload limit on any plan. Serving the wasm counts toward Fast Data Transfer; immutable caching means repeat visitors re-use the browser copy.