NexusNEXUS
Get started
BITCOINCARDANOMIDNIGHT
Bitcoin API for UTXOs, fees, ordinals, and runes

Addresses, mempool, and broadcast over REST. No node to run.

Start the 7-day Builder trialRead the Bitcoin docs
NEXUS
one endpoint, every primitive
Addresses & UTXOsBTC
GET/addresses/{a}/balance58,942 sats
GET/addresses/{a}/utxos3 unspent
GET/addresses/{a}/txs2,020 txs
confirmed + mempool · paged by height
Fees & MempoolBTC
3.2 fast2.1 med1.4 slowsat/vB
mempool 14,208 tx · 8.4 vMB
Ordinals & RunesBTC
GET /addresses/{a}/ordinals
#82,441,907 +2
UNCOMMON•GOODS12,400
3 inscriptions · 2 runes
BroadcastREST
POST /txs/submit
{ "rawTxHex": "0200…" }
txid4f9c…d21a
400 rejected · 409 already in chain

Nexus Bitcoin API at a glance

Mainnet + testnet4

the same endpoints on both networks, each with its own scoped key

bitcoind + electrs + ord

node, address index, and ordinals index, run by us so you do not have to

sat/vB

fee estimates keyed by confirmation target, from 1 block to 1,008

OpenAPI 3.1

machine-readable spec published at /v3/api-docs

Public

status page with live health for core subsystems

Bitcoin chain access: UTXOs, fees, ordinals, and runes over REST

Nexus is a hosted Bitcoin data API: REST over plain HTTPS on top of bitcoind, electrs, and ord, so you query addresses, fees, ordinals, and runes without running a node. The same base URL and X-Api-Key header as Cardano and Midnight, with an OpenAPI 3.1 spec that generates typed clients.

Six endpoint groups cover what a Bitcoin app reads and writes. The same endpoints serve mainnet and testnet4, each with its own scoped key.

# Confirmed balance and UTXOs for a Bitcoin address
BASE="https://nexus.gerowallet.io/api/btc"
ADDR="bc1p..."

curl "$BASE/addresses/$ADDR/utxos" \
  -H "X-Api-Key: nxs_your_api_key_here"

The key decides the network: a mainnet key reads mainnet, a testnet4 key reads testnet4. Each key is scoped to one chain and one network.

Addresses

Chain and mempool stats, confirmed balance in sats, UTXOs (full or paged by height), and transaction history.

View in docs

Transactions

Look up a transaction by txid, fetch its raw hex, batch lookups, and broadcast a signed transaction.

View in docs

Blocks and chain tip

Recent blocks, a block by hash or height, the chain tip, and the latest block.

View in docs

Fees and mempool

Fee-rate estimates in sat/vB by confirmation target, and a mempool snapshot with count, vsize, and fee histogram.

View in docs

Ordinals

Inscription metadata by ID, and the inscriptions held at an address with their UTXO context.

View in docs

Runes

Rune metadata by ID or spaced name, and rune balances by address, by outpoint, or for up to 250 outpoints in one call.

View in docs

The four calls most Bitcoin apps make

Read what an address holds, price the fee, broadcast, and see what is inscribed. Each one is a single request.

Get the UTXOs for a Bitcoin address

As a Bitcoin UTXO API, GET /addresses/{address}/utxos returns every unspent output with its txid, vout, value in sats, and confirmation status, mempool outputs included. For wallets that sync incrementally, /utxos/page pages the same set by block height and returns the tip it read, so you store one watermark and never miss a block. /balance gives the confirmed balance in sats on its own.

curl "$BASE/addresses/$ADDR/utxos" -H "X-Api-Key: nxs_your_api_key_here"

# [{"txid":"c1e9…66de","vout":0,"value":546,
#   "status":{"confirmed":true,"blockHeight":897931}}]
View in docs

Estimate Bitcoin fees in sat/vB

GET /fees returns fee-rate estimates in sat/vB keyed by how many blocks you are willing to wait, from 1 to 1,008. Pick the target that matches your urgency. For a view of the queue itself, the mempool API (GET /mempool) returns the transaction count, total vsize, total fees, and a fee histogram.

curl "$BASE/fees" -H "X-Api-Key: nxs_your_api_key_here"

# {"estimates":{"1":1.07,"3":1.0,"6":0.12,"144":0.12}}
View in docs

Broadcast a signed Bitcoin transaction

POST /txs/submit takes the signed transaction as hex and broadcasts it through our bitcoind, returning the txid. Node rejections come back as clear HTTP errors: an invalid or rejected transaction is a 400, and one already in the chain is a 409. Your keys never leave your app; Nexus only relays the signed bytes.

curl -X POST "$BASE/txs/submit" -H "X-Api-Key: nxs_your_api_key_here" \
  -H "Content-Type: application/json" \
  -d '{"rawTxHex":"0200000001…"}'

# {"txid":"4f9c…d21a"}
View in docs

Read ordinals inscriptions and rune balances

GET /addresses/{address}/ordinals returns the inscription IDs and rune balances held at an address, straight from our ord index, so one ordinals and runes API covers both. /ordinals/inscriptions/{id} returns an inscription's number, content type, and current location, and /ordinals/runes/{rune} takes a rune ID or its spaced name, such as UNCOMMON•GOODS.

curl "$BASE/addresses/$ADDR/ordinals" -H "X-Api-Key: nxs_your_api_key_here"

# {"address":"bc1q…","inscriptions":["71fc…1ad6i0", …],
#  "runesBalances":[…],"satBalance":37442392}
View in docs

Further reading: Bitcoin data infrastructure: node, indexer or API? · Bitcoin runes and ordinals API

Partners, customers, and design partners

  • FluidTokens

    Design partner

  • BloxBean

    Open-source partner

  • Midnight

    Network partner

  • SongMarketCap

    Integration partner

  • Cardano Foundation

    Community integration partner

Flat Bitcoin API pricing

Flat monthly plans instead of per-call metering. Plans start at $9 on Starter, Builder comes with a 7-day trial, and a Bitcoin key is included in every plan's key allowance. Every price is on the pricing page before you sign up.

Starter

$9/mo

  • 3M requests / month
  • 10 req/s
  • 2 API keys
  • Core API only

Prototypes and hobby projects.

Builder

7-day trial

$29/mo

  • 10M requests / month
  • 25 req/s
  • 4 API keys

Indie devs and side projects.

Growth

$79/mo

  • 30M 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, from Builder up. Bundles: Data $19, Build + AI $19, Complete $29. WebSocket packages start at $29 per month.

Start the 7-day Builder trialSee full pricing

Bitcoin API questions, answered

What developers ask before putting Nexus behind a Bitcoin app.

What is the Nexus Bitcoin API?

A hosted Bitcoin blockchain API over REST. Instead of running bitcoind, an address index, and an ordinals index yourself, you call Nexus endpoints for address balances and UTXOs, transactions, blocks, fee estimates, the mempool, ordinals inscriptions, and runes, and you broadcast signed transactions through the same API. Authentication is an nxs_ API key in the X-Api-Key header, the same as Nexus's Cardano and Midnight APIs.

Which Bitcoin networks does Nexus support?

Mainnet and testnet4, with the same endpoints on both. Each network runs its own bitcoind and electrs. The network comes from the API key: a mainnet key reads mainnet and a testnet4 key reads testnet4, so you issue one key per network from the same account.

Do you index ordinals and runes?

Yes. Nexus runs the ord indexer, so you can read an inscription by ID, list the inscriptions and rune balances held at an address, look up a rune by ID or spaced name, and check which inscriptions and runes sit on a given UTXO, for up to 250 outpoints in one call.

Can I broadcast Bitcoin transactions?

Yes. POST /api/btc/txs/submit takes a signed transaction as hex and broadcasts it through our node, returning the txid. You sign in your own app; Nexus never sees a private key. Rejections from the node come back as HTTP errors with the reason: 400 for an invalid or rejected transaction, 409 if it is already in the chain.

How do keys work across Bitcoin, Cardano, and Midnight?

One account, one dashboard, one bill, with a key per chain and network. A team that already uses Nexus for Cardano adds Bitcoin by issuing a Bitcoin key; the base URL and the X-Api-Key header stay the same. Every key counts toward the plan's key allowance.

How much does the Bitcoin API cost?

The same flat monthly plans as the rest of Nexus: Starter $9, Builder $29 with a 7-day trial, Growth $79, Scale $199, Enterprise $499, each with a monthly request allowance and a rate limit rather than per-call metering. Dedicated infrastructure is available on request.

Ship your Bitcoin app without running a node

UTXOs, fees, the mempool, ordinals, runes, and broadcast, with a key for each network. Plans from $9 a month.

Start the 7-day Builder trialTalk to us about Enterprise or Dedicated

Dedicated infrastructure starts at $2,000 per month. A contractual SLA is available on Dedicated: contact sales.