eth_syncing - zkSync RPC Method
Check the sync status of your zkSync Era node. Returns sync progress or false when fully synced — essential for node health monitoring and dApp reliability.
Returns the sync status of your zkSync Era node — either false when fully synced, or an object describing the sync progress.
Why zkSync? Build on Matter Labs' flagship zkEVM powering the Elastic Network of interoperable hyperchains with ZK Stack modular framework, hyperchain interoperability, native account abstraction, and $1.9B in tokenized real-world assets.
When to Use This Method
eth_syncing is essential for ZK developers, RWA tokenization teams, and builders launching custom L2/L3 chains:
- Node Health Checks — Verify your node is fully synced before processing transactions
- Sync Progress Monitoring — Track how far behind your node is during initial sync or after downtime
- Load Balancer Routing — Route requests only to fully synced nodes in multi-node setups
- dApp Reliability — Display sync warnings to users when data may be stale
Code Examples
Common Use Cases
1. Node Health Monitor
Continuously check sync status and alert on issues:
async function monitorNodeHealth(provider, interval = 30000) {
setInterval(async () => {
const syncing = await provider.send('eth_syncing', []);
if (syncing === false) {
const blockNumber = await provider.getBlockNumber();
const block = await provider.getBlock(blockNumber);
const age = Date.now() / 1000 - block.timestamp;
if (age > 60) {
console.warn(`Node synced but block is ${age.toFixed(0)}s old`);
} else {
console.log(`Healthy — block ${blockNumber}`);
}
} else {
const current = parseInt(syncing.currentBlock, 16);
const highest = parseInt(syncing.highestBlock, 16);
console.warn(`Syncing: ${highest - current} blocks behind`);
}
}, interval);
}2. Wait for Sync Before Processing
Block application startup until the node is ready:
async function waitForSync(provider, pollInterval = 5000) {
while (true) {
const syncing = await provider.send('eth_syncing', []);
if (syncing === false) {
console.log('Node synced — ready to process transactions');
return;
}
const current = parseInt(syncing.currentBlock, 16);
const highest = parseInt(syncing.highestBlock, 16);
console.log(`Waiting for sync: ${highest - current} blocks remaining...`);
await new Promise(r => setTimeout(r, pollInterval));
}
}Error Handling
| Error Code | Description | Solution |
|---|---|---|
| -32603 | Internal error | Node may be starting up — retry after delay |
| -32005 | Rate limit exceeded | Reduce polling frequency |
Related Methods
eth_blockNumber— Get current block heightnet_peerCount— Check peer connectionsnet_listening— Verify node is accepting connectionsweb3_clientVersion— Get node client info