| RU (Request Unit) | The billing unit for API calls. Different RPC methods consume different amounts of RU. For example, eth_chainId costs 0 RU while eth_getLogs costs 50 RU. |
| Endpoint | A blockchain access point consisting of an RPC URL and API key. Each endpoint is tied to a specific chain. |
| API Key | A unique identifier generated for each endpoint. Used to authenticate your requests. |
| Chain | A blockchain network (e.g., Ethereum Mainnet, Base, BSC). |
| JSON-RPC | The standard protocol for communicating with blockchain nodes. BlockReq supports JSON-RPC 2.0. |
| HTTPS | Secure HTTP endpoint for standard request-response RPC calls. |
| WSS | WebSocket Secure endpoint for persistent connections and real-time subscriptions (e.g., eth_subscribe). |
| Archive Data | Historical blockchain state data. Required for methods like eth_getBalance at past block heights. Available on Growth and Premium plans. |
| Rate Limit | The maximum number of RU per second your plan allows. Free plan: 1,000 RU/sec; Premium: 5,000 RU/sec. |
| Free Refresh | Monthly automatic replenishment of 80M RU for free-tier users. |
| Balance | Your current RU credit balance, consumed as you make API calls. |
