durable-local

Named durable values for the browser.

A TypeScript library that gives a browser tab one thing: an application value that survives close and reload. No database, no state manager, no sync engine. The application owns the value. The package owns its survival.

Install

pnpm add @0xsarwagya/durable-local

Use

import { createDurable } from "@0xsarwagya/durable-local";

const durable = createDurable();

const workspace = await durable.open("workspace", {
  initial: { title: "Untitled", blocks: [] },
});

workspace.value; // { title: "Untitled", blocks: [] }

await workspace.update((current) => ({
  ...current,
  title: "Something",
}));

// Close the tab. Come back tomorrow. Still there.

Every commit is atomic — subscribers only see values that survived a successful IndexedDB transaction. Cross-tab observation is built in.

Boundaries

• Not a database. No queries, collections, indexes, joins.
• Not a state manager. No actions, reducers, middleware.
• Not sync. State stays on the device; the package does not touch the network.
• Not encryption. Storage is not confidentiality.

If you need any of those, this package is not what you want.

Guarantees

• Committed values survive reload.
• Failed writes preserve the previous committed value.
• Concurrent updates do not silently overwrite one another.
• Migration failure preserves the previous committed value.
• Cross-tab commits are eventually observed.
• Invalid stored state is never returned as T.

Browsers

Runs on IndexedDB. Tested on every commit in Chromium, Firefox, and WebKit via Playwright.

Docs and demo

• Docs: https://oss.sarwagya.wtf/durable-local/docs
• Demo: https://oss.sarwagya.wtf/durable-local/demo

License

MIT.