API reference, Chain & reference
Gas stream
- Elysium: Each new Elysium block's base fee, gas used and tips, from our node; the history is GET /v1/gas.
- HyperEVM: Each new HyperEVM block's base fee, gas used and tips, from our node; the history is GET /v1/gas.
- Not on HyperCore: HyperCore has no gas: its actions pay fixed exchange fees (POST /info userFees)
WebSocket channel elysium.gas on wss://api.femtos.xyz/v1/ws | WebSocket channel hyperevm.gas on wss://api.femtos.xyz/v1/ws
Subscribe
Elysium
{"op":"subscribe","channel":"elysium.gas","filter":{}}HyperEVM
{"op":"subscribe","channel":"hyperevm.gas","filter":{}}Key: Authorization: Bearer $FEMTOS_KEY. Get a free key, or with no browser through agent onboarding.
Response fields
| Field | Type | Meaning |
|---|---|---|
data | GasBlock | one Elysium block per message, within a second of our node: {block, time, kind, baseFee, gasUsed, gasLimit, txs, tipP50, tipP90} (Elysium) |
data.kind | small | big | block | small / big: HyperEVM's two block kinds, each with its own base fee and mempool (small: 3M gas, about one a second; big: 30M gas, about one a minute; a gas limit above 10M is big); block: Elysium's one kind |
data.baseFee | decimal | Base fee per gas, wei |
data.tipP50 | decimal | null | Median priority fee of its transactions, wei; null while unknown (tips of the history are read from the node after a restart) |
data.tipP90 | decimal | null | 90th percentile priority fee of its transactions, wei; null while unknown (tips of the history are read from the node after a restart) |
data | GasBlock | one HyperEVM block per message, small and big blocks alike (`kind`), within a second of our node: {block, time, kind, baseFee, gasUsed, gasLimit, txs, tipP50, tipP90} (HyperEVM) |
Related: Chain & reference
- Freshness GET /v1/status Elysium, HyperCore, HyperEVM
Head and lag of each layer, measured now. - Freshness stream WS status Elysium, HyperCore, HyperEVM
The GET /v1/status answer (head and lag of each layer, live feeds), pushed whole on subscribe and at most once a second when it changes. - Blocks stream WS elysium.blocks | hyperevm.blocks Elysium, HyperEVM
Each new HyperEVM block header, small and big blocks, from our node. - Gas tracker GET /v1/gas Elysium, HyperEVM
Every HyperEVM block's base fee, gas used and tips over 1h to 7d, with stats and the latest block. - Block GET /v1/blocks/{number} Elysium, HyperEVM
One HyperEVM block and every transaction in it: who called what, swaps, gas and fees. - 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.
More
- This page as Markdown
- The whole API reference
- What Elysium serves
- What HyperEVM serves
- The whole API in one Markdown file
- OpenAPI 3.1 document
Agent guide (agents.md)llms.txtOpenAPIMCP serverGet an API keyChangelog