API reference · Chain & reference

Blocks stream

Not on HyperCore: HyperCore’s blocks are its exchange state: every hc.* frame carries its height, GET /v1/status its head

WebSocket channel elysium.blocks on wss://api.femtos.xyz/v1/ws · WebSocket channel hyperevm.blocks on wss://api.femtos.xyz/v1/ws

Elysium

{"op":"subscribe","channel":"elysium.blocks","filter":{}}

HyperEVM

{"op":"subscribe","channel":"hyperevm.blocks","filter":{}}

Key: Authorization: Bearer $FEMTOS_KEY. Get a free key, or with no browser through agent onboarding.

Response fields

Field	Type	Meaning
`data`	ElysiumBlock	one Elysium block per message: {number, hash, parent_hash, timestamp, tx_count, gas_used, base_fee, l1_block_number} (Elysium)
`data.timestamp`	int	block time (s)
`data`	HyperevmBlock	one HyperEVM block per message, small and big blocks alike (about one a second): {number, hash, parent_hash, timestamp, tx_count, system_tx_count, gas_used, gas_limit, base_fee} (HyperEVM)
`data.gas_limit`	int	Gas limit: 3 M for a small block (about one a second), 30 M for a big one (about one a minute) (HyperEVM)
`data.system_tx_count`	int	System transactions: HyperCore -> HyperEVM transfers credited (HyperEVM)

Freshness GET /v1/status Elysium, HyperCore, HyperEVM
Head and lag of each layer, measured now.
Transaction GET /v1/tx/{hash} Elysium, HyperEVM
One transaction: status, gas, decoded transfers, swaps and liquidity, bridge legs and journey.
Elysium RPC POST /v1/elysium/rpc Elysium
Free public Elysium mainnet RPC by Femtos (chain 99901), no key, read only (no transaction sending), for wallets and dapps, not for indexing (use the Femtos API for history): per IP 5 requests a second and 60 a minute, batches of 5, eth_getLogs over 1,000 blocks at most, state of the last 128 blocks only.
Stream stats WS stats HyperCore
Our HyperCore stream health, once a second.
Check your key GET /v1/whoami Elysium, HyperCore, HyperEVM
Answers the name your key is registered under, its tier, billing state and the limits in force.
OpenAPI document GET /v1/openapi.json Elysium, HyperCore, HyperEVM
The OpenAPI 3.1 contract of every REST call, public.