eth_syncing

eth_syncing reports whether an Avalanche C-Chain node is still catching up to the chain tip or has finished syncing. When the node is fully synced it returns false; while it is importing blocks it returns an object with startingBlock, currentBlock, and highestBlock so you can gauge how far behind it is. On the C-Chain — the EVM chain where AVAX pays for gas, secured by Snowman/Avalanche consensus — a node must be fully synced before its responses to balance, log, and call queries can be trusted. Send the request to https://avalanche.therpc.io/YOUR_API_KEY (chain ID 43114, 0xa86a) to confirm a node is current before you depend on its data.

Use cases

• Verify that a freshly started C-Chain node has caught up before adding it to a load balancer and routing AVAX traffic to it.
• Compute a sync progress percentage from currentBlock and highestBlock and surface it on a node-monitoring dashboard.
• Gate application startup on a false response so your service only begins serving requests once the node is fully synced.
• Diagnose a stuck or slow node by polling currentBlock over time — on the C-Chain, with its one-to-two-second block cadence, a currentBlock that barely advances signals a problem.

Parameters

This method takes no parameters. Pass an empty array [].

Response

Example request

1curl https://avalanche.therpc.io/YOUR_API_KEY \
2  -X POST \
3  -H "Content-Type: application/json" \
4  -d '{
5    "jsonrpc": "2.0",
6    "method": "eth_syncing",
7    "params": [],
8    "id": 1
9  }'

Try it live in the Avalanche playground.

Errors & troubleshooting

Common pitfalls

• Some clients can report false during certain sync phases even when they are not truly at the tip (for example Beam Sync on Nethermind). Do not treat false alone as a hard guarantee of full sync; cross-check eth_blockNumber against a known-good source.
• This call reports execution-layer (EVM) sync only. Avalanche's consensus is handled by the Snowman/Avalanche engine inside AvalancheGo, so node-level consensus health is observed separately, not through this execution-layer method.
• The returned object shape varies by client — Geth includes snap-sync counters, Erigon adds stage fields — so code that reads optional keys should handle missing fields gracefully rather than assume a fixed schema.

Supported networks

• Mainnet — Chain ID: 43114
• Fuji

See also

• eth_blockNumber
• eth_chainId
• net_peerCount

1curl https://avalanche.therpc.io/YOUR_API_KEY \
2  -X POST \
3  -H 'Content-Type: application/json' \
4  -d '{"jsonrpc":"2.0","id":1,"method":"eth_syncing","params":[]}'