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Version: 0.17

Sync and store

Every operation the Web SDK performs reads from — or writes to — a local store. This page covers how to keep that store in sync with the Miden network, and how to back up / restore the store itself.

client.sync()​

Fetches private notes from the Note Transport Layer, then pulls onchain updates from the Miden node and applies them to the local store. Returns a SyncSummary describing what changed. A note-transport failure is logged and chain sync continues; call client.notes.fetchPrivate() directly when you need to detect a transport error.

import { MidenClient } from "@miden-sdk/miden-sdk";

const client = await MidenClient.createTestnet();

const summary = await client.sync();

console.log("Block:", summary.blockNum());
console.log("Committed notes:", summary.committedNotes().length);
console.log("Consumed notes:", summary.consumedNotes().length);
console.log("Committed txs:", summary.committedTransactions().length);
console.log("Updated accounts:", summary.updatedAccounts().length);

SyncSummary accessors:

  • blockNum(): number — tip block the summary is based on.
  • committedNotes(): NoteId[] — notes committed in this sync window.
  • consumedNotes(): NoteId[] — notes consumed in this sync window.
  • committedTransactions(): TransactionId[] — transactions that were committed.
  • updatedAccounts(): AccountId[] — accounts whose onchain state advanced.

Timeout handling​

const summary = await client.sync();

client.sync() does not take a timeout option. If a UI needs a wall-clock timeout, wrap the promise at the application layer.

Auto-sync on creation​

The network factories (createTestnet, createDevnet) default autoSync: true, so one sync runs before the client is returned. create() defaults to false; pass autoSync: true explicitly if you want the same behaviour for a custom endpoint:

const client = await MidenClient.create({
  rpcUrl: "localhost",
  autoSync: true,
});

Current sync height​

Cheap check of the locally-known tip, no network call:

const height: number = await client.getSyncHeight();
console.log("Local tip:", height);

Fee faucet​

The chain's fee faucet comes from its synced protocol configuration:

await client.sync();
const feeFaucet = await client.feeFaucetId();

BlockHeader no longer exposes feeFaucetId(). Sync before querying it unless you supplied the optional feeFaucetId client option.

Store backup and restore​

The SDK exposes two standalone functions (not methods on MidenClient) for snapshotting the entire store:

import { exportStore, importStore } from "@miden-sdk/miden-sdk";

// Dump the store identified by storeName into a JSON string.
const storeName = await client.storeIdentifier(); // or pass your own storeName
const dump = await exportStore(storeName);

// Later — on another device, or after a page refresh — restore it.
await importStore(storeName, dump);
  • exportStore(storeName) → Promise<string> — returns a JSON dump of the IndexedDB store.
  • importStore(storeName, dump) → Promise<void> — replaces all existing data in the target store with the dump.

importStore is destructive. It overwrites the target store entirely — keep a backup if you need the previous state.

These helpers are package-level exports, not methods on MidenClient, so they can run without an active client — for example in a worker that performs scheduled backups.

Next​

  • Testing — running a deterministic, in-memory mock chain for tests.
  • Transactions — how network state feeds back into transaction flows.