> ## Documentation Index > Fetch the complete documentation index at: https://docs.blockscout.com/llms.txt > Use this file to discover all available pages before exploring further. # Get Estimated Block Countdown Time by Block Number > Returns the estimated time remaining, in seconds, until a certain block is mined `blockno` must be a block that has not been mined yet. A block that already exists returns an error. ## OpenAPI ````yaml /openapi-specs/pro-rpc-api-universal.json get /v2/api?module=block&action=getblockcountdown openapi: 3.1.0 info: title: 'Blockscout PRO API: RPC and ETH RPC' version: 2.0.0 description: > Blockscout's Etherscan-compatible RPC API and standard ETH JSON-RPC methods, served from the multichain PRO API. ## Base URL All requests go to `https://api.blockscout.com`. Choose the network with `chain_id` (for example `1` for Ethereum or `8453` for Base). ## Authentication A PRO API key is required on every request, including the free tier. Get one at [dev.blockscout.com](https://dev.blockscout.com). Send it as the `apikey` query parameter or as an `Authorization: Bearer YOUR_KEY` header. See [API rate limits](https://docs.blockscout.com/rate-limits) for plan limits. Requests without a key are not served: the API responds with HTTP `402`. To call without an API key, pay per call with [x402 payments](https://docs.blockscout.com/devs/x402-payments). ## RPC API (module and action) Etherscan-style requests. Pass `chain_id`, `module` and `action`: ``` https://api.blockscout.com/v2/api?chain_id=1&module=account&action=balance&address=0x...&apikey=YOUR_KEY ``` The same calls are also available at `https://api.blockscout.com/{chain_id}/api?module=...&action=...`. ## ETH RPC API (JSON-RPC) Standard Ethereum JSON-RPC methods use `POST` requests: ``` POST https://api.blockscout.com/{chain_id}/json-rpc Content-Type: application/json Authorization: Bearer YOUR_KEY {"jsonrpc":"2.0","method":"eth_blockNumber","params":[],"id":1} ``` ## Migrating from Etherscan Replace the base URL with `https://api.blockscout.com/v2/api` and rename `chainid` to `chain_id`. Module and action names are the same for most calls. license: name: MIT url: https://opensource.org/licenses/MIT contact: name: Blockscout Community url: https://discord.gg/blockscout servers: - url: https://api.blockscout.com security: - bearerAuth: [] - apiKeyAuth: [] tags: - name: Account description: Account-related endpoints - name: Block description: Block-related endpoints - name: Contract description: Smart contract-related endpoints - name: Logs description: Event logs endpoints - name: Stats description: Network statistics endpoints - name: Token description: Token-related endpoints - name: Transaction description: Transaction-related endpoints - name: ETH RPC description: Ethereum JSON-RPC compatible endpoints externalDocs: url: https://docs.blockscout.com/devs/apis/rpc paths: /v2/api?module=block&action=getblockcountdown: get: tags: - Block summary: Get Estimated Block Countdown Time by Block Number description: > Returns the estimated time remaining, in seconds, until a certain block is mined `blockno` must be a block that has not been mined yet. A block that already exists returns an error. operationId: get-estimated-block-countdown parameters: - $ref: '#/components/parameters/chain_id_query' - $ref: '#/components/parameters/module_block' - $ref: '#/components/parameters/action_getblockcountdown' - in: query name: blockno schema: type: integer required: true description: Target block number responses: '200': description: Block countdown retrieved successfully content: application/json: schema: oneOf: - allOf: - $ref: '#/components/schemas/ResponseOK' - type: object properties: result: type: object properties: currentBlock: type: string countdownBlock: type: string remainingBlock: type: string estimateTimeInSec: type: string - $ref: '#/components/schemas/ResponseNOTOK' headers: x-credits-remaining: description: >- Number of credits remaining in your plan. Resets daily on the free plan, monthly otherwise. schema: type: integer x-ratelimit-limit: description: >- Available requests per second with your plan. Returns -1 on internal error. schema: type: integer x-ratelimit-remaining: description: >- Remaining rate limit based on your queries. Returns -1 on internal error. schema: type: integer x-ratelimit-reset: description: >- Time in milliseconds until the rate limit resets. Returns -1 on internal error. schema: type: integer externalDocs: url: https://docs.blockscout.com/devs/apis/rpc/block components: parameters: chain_id_query: name: chain_id in: query required: true description: The ID of the blockchain schema: type: string example: '1' module_block: name: module in: query required: true schema: type: string enum: - block description: Module name (must be 'block') action_getblockcountdown: name: action in: query required: true schema: type: string enum: - getblockcountdown schemas: ResponseOK: type: object properties: status: type: string enum: - '1' description: Status code (1 = OK) message: type: string example: OK description: Response message ResponseNOTOK: type: object properties: status: type: string enum: - '0' description: Status code (0 = Error) message: type: string example: NOTOK description: Error message result: type: string nullable: true description: Error details securitySchemes: bearerAuth: bearerFormat: JWT description: API key passed as a Bearer token in the Authorization header. scheme: bearer type: http apiKeyAuth: description: API key passed as the `apikey` query parameter. in: query name: apikey type: apiKey ```` This documentation is built and hosted on [Mintlify](https://mintlify.com), a developer documentation platform.