The full-stack
Cardano API
chain data, market data, and transactions on one surface
{ "height": 13768412, "epoch": 646, "slot": 193760112, "tx_count": 27 }
▸ nexus.address_utxos address: addr1q…9fzk
Six products on one API
Each API key is scoped to one chain and one network. Market data, wallet analytics, transaction building, and MCP are add-ons.
Blockchain API
Blocks, txs, addresses & assets
Ten endpoint groups, accounts to governance, plus submit and evaluate.
WebSocket Streaming
Live blocks & txs, pushed to you
Push, not poll: market data on a 10 second cadence, Blueprints with REST backfill.
Transaction Building
Build & submit on-chain
Transfers, staking, and Conway governance built server-side. Unsigned CBOR out; keys never touch Nexus.
DEX Aggregator
Best-price swap routing
Best-price routing across Minswap, WingRiders, Splash, and SaturnSwap. You sign every swap.
MCP Server
Nexus data for AI agents
A hosted MCP endpoint: AI agents query Cardano, Bitcoin, and Midnight with your own key.
Market Data
Prices, pools & tokens
Prices, candles, pools, order books, and NFT sales across all 11 indexed DEXes.
Nexus Cardano API at a glance
Cardano DEXes indexed for first-party market data
Cardano networks on the same endpoints: mainnet, preprod, preview
failover across Yaci, Koios, Blockfrost, and our own indexers
machine-readable spec published at /v3/api-docs
status page with live health for core subsystems
Cardano chain data: every endpoint group on one REST API
A Cardano REST API over plain HTTPS, with an OpenAPI 3.1 spec so you can generate a typed client in any language with one command.
Ten endpoint groups cover the chain end to end. The same endpoints serve mainnet, preprod, and preview, each with its own scoped key.
# Transaction history for a Cardano address, mainnet
BASE="https://nexus.gerowallet.io/api"
ADDR="addr1q9x2..."
curl "$BASE/addresses/$ADDR/transactions/history?network=mainnet" \
-H "X-Api-Key: nxs_your_api_key_here"One auth header, one ?network= parameter: mainnet, preprod, and preview on the same endpoints. Each key is scoped to one chain and one network.
Addresses
Balances, UTXOs, and full transaction history, including payment-credential and slot-window queries.
View in docsEpochs and parameters
Epoch summaries and the live protocol parameters that price your transactions.
View in docsPools, enriched
Stake pool queries with ticker, ROS, and metadata from a dedicated chain-data pipeline.
View in docsDReps and governance
DReps, governance proposals, votes, the constitutional committee, and the constitution.
View in docsTransactions
A rich single-call transaction object, batch endpoints, and raw CBOR when you need the bytes.
View in docsSubmit and evaluate
Broadcast signed transactions and evaluate execution units before you spend.
View in docsCardano WebSocket API: live streaming and Blueprints
Subscribe over WebSocket for live chain and market events, on the same account and the same base URL as your chain reads.
WebSocket streaming
Push, not poll.
- One connection
- Hold a single socket instead of firing thousands of requests.
- 10 second cadence
- Market-data topics broadcast on a fixed interval.
- Capacity of its own
- Connection and message allowances come as WebSocket packages you attach to a plan, so streaming scales independently of your REST quota.
Blueprints
Describe what to watch. Nexus delivers the matching events.
- Self-serve
- On-chain event streams you define yourself.
- UTXO or TRANSACTION
- Pick the granularity your consumer actually needs.
- REST backfill on every stream
- Reconnect and replay exactly the events you missed, instead of resyncing from scratch.
Streaming pipelines break on reconnect, not on the happy path.
Backfill is what makes an event stream safe to build settlement logic on.
Streaming endpoints and Blueprint schemas are documented in the API reference.
First-party Cardano market data on the same API
Chain-data APIs like Blockfrost and Koios do not serve DEX market data. The market-data specialists we know of do not serve chain data.
Nexus serves both. One base URL, one auth header: read a UTXO, then read the candle chart for the token inside it.
Market Data add-on: 11 Cardano DEXes indexed first-party, normalized into one surface.
Prices and OHLCV candles
Spot prices and candle history for tokens on every indexed DEX.
Pools, TVL, and reserves
Liquidity pool state, total value locked, and reserve balances per pair.
Orderbooks and swaps
Order flow and executed swaps, normalized across venues.
Top traders
Most active addresses per token and per pool.
NFT collections and sales
Collections, floor prices, and individual sales.
ADA/USD candles
Fiat reference candles so charts and P&L resolve to dollars.
FIFO wallet P&L, built in
The Wallet Analytics add-on turns any Cardano address into holdings, transaction history, and FIFO cost-basis P&L.
Portfolio views and tax-season exports come from the API, not from an indexer you build and babysit.
Comparing providers? See the Nexus vs Blockfrost comparison, or browse the market data and wallet endpoints in the API reference.
Cardano transaction builder API: build and submit server-side
Nexus builds the transaction. Your users sign it with their own keys. Non-custodial by construction: private keys never reach Nexus.
Build
Three transaction families, assembled server-side.
- Transfers
- ADA and native tokens, with UTXO selection and fee calculation server-side.
- Staking
- Pool delegation and reward withdrawals, as standard certificates.
- Governance
- Conway DRep delegation and votes, not just reading governance state.
Sign and submit
Your users sign. Nexus broadcasts.
- Returns
- Unsigned CBOR, ready for any wallet to sign.
- Submit
- Broadcast the signed transaction through the same API.
- Evaluate
- Script execution units, before you commit to fees.
Request and response shapes for every builder endpoint are in the API reference.
Conway governance coverage: DReps, proposals, votes
Cardano governance is on-chain state like any other, and Nexus treats it that way: read governance state and act on it through the same API.
The read side covers the full Conway surface. The write side adds builder support for the two governance actions most apps need.
Read governance state
- DReps: list, detail, delegators, and voting history
- Governance proposals and their lifecycle
- Votes, by proposal and by voter
- The constitutional committee
- The constitution itself
Act on it
- DRep delegation certificates, built server-side as unsigned CBOR
- Governance votes, ready for your wallet flow to sign and submit
A governance dashboard, a DRep explorer, or a wallet voting flow can run its reads and its writes against one provider, one base URL, and one spec.
Cardano data infrastructure built for production
One endpoint in front of every upstream. Per-provider health checks send each request to a healthy source, so one provider's incident does not become your outage.
Multi-provider failover
Redundancy is the architecture, not an add-on.
- Our own indexers
- Yaci
- Koios
- Blockfrost
Health checks pick a healthy upstream per request.
Keys scoped per chain and network
Promoting from testnet swaps the key and one parameter, not your code.
- Scope
- One chain, one network per key
- Networks
- mainnet, preprod, preview
- Switch
?network=on the same endpoints
Public status page
Live health for our core subsystems, published for everyone. Check the status page any time.
Add-ons for Cardano builders
- Hosted MCP server. Connects Claude and other AI agents to Nexus data and tools.
- IPFS. Resolve, inspect, and pin content through our self-hosted node.
Flat Cardano API pricing
Flat monthly plans instead of per-call metering, so the bill does not spike with your traffic. There is no free tier: Builder comes with a 7-day trial instead, and every price is on the pricing page before you sign up.
Builder
7-day trial$29/mo
- 2M requests / month
- 25 req/s
- 4 API keys
Indie devs and side projects.
Growth
$79/mo
- 10M requests / month
- 50 req/s
- 7 API keys
Startups and DApp teams.
Scale
$199/mo
- 50M requests / month
- 100 req/s
- 13 API keys
Production applications.
Enterprise
$499/mo
- 200M requests / month
- 500 req/s
- Unlimited API keys
Exchanges, aggregators, and institutional users.
Add-ons: Market Data $19, Wallet Analytics $15, Transaction Builder $19, MCP Server $19, IPFS $5 per month. WebSocket packages start at $29 per month.
Cardano API questions, answered
What developers ask before putting Nexus behind a Cardano app.
What is a Cardano data API?
A Cardano data API is a hosted service that indexes the Cardano blockchain and exposes its state (addresses, transactions, assets, pools, governance) over REST endpoints, so you do not run cardano-node and db-sync yourself. Nexus goes further than chain data: the same Cardano endpoints and auth header also serve first-party DEX market data, FIFO wallet P&L, and a server-side transaction builder as opt-in add-ons, plus live WebSocket streaming.
Can I query Cardano without running a node?
Yes. That is the job of a hosted Cardano API: Nexus operates the indexing infrastructure, with multi-provider failover across our own indexers, Yaci, Koios, and Blockfrost, and you read the chain over plain HTTPS with an nxs_ API key in the X-Api-Key header. No cardano-node to run, no db-sync to keep in sync. The OpenAPI 3.1 spec at /v3/api-docs generates a typed client in your language.
What Cardano endpoints does Nexus cover?
Chain data covers accounts, addresses, assets and holders, blocks, epochs and protocol parameters, enriched stake pools, DReps and governance, scripts and datums, rich transaction objects, and transaction submit plus evaluate. On top of that, the same base URL and auth header serve DEX market data across 11 DEXes, NFT sales, wallet P&L, and transaction building as opt-in add-ons, with WebSocket streaming as its own package. The full reference with request and response shapes lives at /docs.
How is Nexus different from Blockfrost, Koios, or Maestro on Cardano?
Those providers cover on-chain Cardano data well. Nexus adds first-party DEX market data across 11 DEXes, NFT sales data, FIFO wallet P&L, a server-side transaction builder, and WebSocket streaming on the same API surface, behind multi-provider failover and flat monthly pricing. One honest caveat: Nexus is not API-compatible with Blockfrost, so migrating means changing endpoint paths (config-level work, not a rewrite), and a migration guide is planned. Read the full Blockfrost comparison.
Which Cardano networks does Nexus support?
Mainnet, preprod, and preview, all on the same endpoints and selected with the ?network= query parameter. Each API key is scoped to one chain and one network, so you issue a preview or preprod key for development and a mainnet key for production, both from the same account and the same dashboard. Promoting means swapping the key and the parameter, not rewriting your data layer.
Does Nexus cover Conway governance data?
Yes. On the read side: DReps, governance proposals, votes, the constitutional committee, and the constitution. On the write side, the transaction builder produces unsigned CBOR for DRep delegation and governance votes, so an application can read governance state and act on it through the same API.
How much does the Nexus Cardano API cost?
Plans are flat monthly prices, not per-call metering: Builder $29 (2M requests/month, 25 req/s), Growth $79 (10M, 50 req/s), Scale $199 (50M, 100 req/s), and Enterprise $499 (200M, 500 req/s). There is no free tier; Builder comes with a 7-day trial instead. Add-ons such as Market Data ($19/mo) and Wallet Analytics ($15/mo) are itemized on the pricing page before you sign up.
Is there a free Cardano API?
Yes. Koios is a free, community-run query layer, Blockfrost has a free STARTER tier of 50,000 requests per day, and Iagon has announced Insight, a free API expected in Q3 2026 covering a roughly 25-endpoint chain-data subset. Nexus is paid only: plans start at Builder, $29 per month with a 7-day trial, and add first-party DEX market data, FIFO wallet P&L, transaction building, and WebSocket streaming, which those chain-data services do not offer.
Ship your Cardano app on one integration
Chain data, market data, wallet P&L, transaction building, and streaming: one account, one bill, multi-provider failover underneath.
Dedicated infrastructure starts at $2,000 per month. A contractual SLA is available on Dedicated: contact sales.