# Active NFT collections · Elysium API · Femtos

> Collections with the most transfers over the last 1 h or 24 h.

- Base URL: `https://api.femtos.xyz/v1` (REST) · `wss://api.femtos.xyz/v1/ws` (WebSocket) · MCP: `https://api.femtos.xyz/mcp`
- Auth: `Authorization: Bearer $FEMTOS_KEY` (or `X-API-KEY: $FEMTOS_KEY`). Free key: https://femtos.xyz/accounts/ (browser), or with
  no browser: `GET https://femtos.xyz/accounts/agent/challenge`, solve its proof of work, then `POST https://femtos.xyz/accounts/agent/signup`
  (https://femtos.xyz/agents.md#agent-onboarding)
- Decimals are exact strings, times Unix milliseconds, addresses lowercase `0x`
- Whole API in one file: https://femtos.xyz/agents.md · OpenAPI: https://api.femtos.xyz/v1/openapi.json · Index: https://femtos.xyz/llms.txt
- Page with live calls: https://femtos.xyz/elysium/nft-collections

## Active NFT collections — GET `/v1/nfts/collections`

Collections with the most transfers over the last 1 h or 24 h.

| Param | In | Example or values |
|---|---|---|
| `layer` | query | `elysium` |
| `window` | query | `24h`, `1h` |
| `limit` | query | `20` |

```bash
curl -H "Authorization: Bearer $FEMTOS_KEY" "https://api.femtos.xyz/v1/nfts/collections?layer=elysium&window=24h&limit=20"
```

| Field | Type | Meaning |
|---|---|---|
| `collections[]` | object | {address, standard, name, symbol, transfers, mints, burns, lastBlock} |
| `from · to` | int | window (ms), ends at the indexed head |
| `fromBlock · toBlock` | int | blocks read |

## Related (NFTs)

- [NFT collection](https://femtos.xyz/elysium/nft-collection.md): Metadata, tokens seen and 24 h activity of one collection.
- [Collection tokens](https://femtos.xyz/elysium/nft-tokens.md): Tokens of a collection by id, with their owner and metadata URI.
- [NFTs of a wallet](https://femtos.xyz/elysium/nft-owned.md): ERC-721 tokens owned and ERC-1155 balances of one address.
- [NFT transfers](https://femtos.xyz/elysium/nft-transfers.md): Transfers of a collection or one token, newest first.

All Elysium endpoints: https://femtos.xyz/elysium.md