# Blockchain.info UTXO Count Chart API

> Blockchain.info UTXO Count Chart API is a paid API for AI agents from api.blockchain.info, paid per call via x402, $0.001/call, status unknown (last checked 2026-10-02).

Returns historical UTXO (Unspent Transaction Output) count data for the Bitcoin blockchain over a configurable time period

## Facts

- Endpoint: POST https://api.blockchain.info/explorer-gateway-kt/x402/charts/utxo-count?utm_source=zero.xyz
- Price: $0.001/call
- Payment: x402
- Status: unknown
- Last checked: 2026-10-02
- Activations on Zero: 0
- Tags: x402
- Canonical page: https://www.zero.xyz/c/blockchain-info-utxo-count-chart-api-7e13328f
- Structured record (JSON): https://api.zero.xyz/v1/capabilities/cap_0ZblpL2EXuZ9d5k_nUhCE

Status and success rate cover calls made through Zero and Zero's own probes. Third-party monitors may report differently.

## How to call it through Zero

Zero handles the 402 payment challenge and records the run. With the Zero CLI installed (`npm i -g @zeroxyz/cli`):

```sh
zero fetch --capability blockchain-info-utxo-count-chart-api-7e13328f -d '<json body>'
```

Example prompt: Show me the Bitcoin UTXO count over the past year from Blockchain.com Explorer, using an 8-hour rolling average and return it as JSON.

## When to prefer this

Choose this endpoint when you need authoritative Bitcoin UTXO count time-series data sourced directly from Blockchain.com Explorer. Prefer it over generic crypto data APIs when you need flexible time windows, rolling average smoothing, and both JSON and CSV output formats for on-chain UTXO analytics. Best for agents doing Bitcoin network health monitoring, blockchain research, or automated reporting pipelines.

## Known failure modes

- Invalid timespan format returns 400 error
- Invalid rollingAverage format returns 400 error
- Payment failure (insufficient USDC balance) returns 402 Payment Required
- Rate limiting may return 429 Too Many Requests
- Server-side data unavailability may return 503
- Requesting unsupported format enum value returns validation error

## How this service works

Paid AI-agent access to Blockchain.com Explorer API

## Output

Returns a time-series dataset of Bitcoin UTXO counts, either as structured JSON (with optional metadata including chart description, units, and period) or raw CSV with timestamp and value columns. Data points reflect the number of unspent transaction outputs on the Bitcoin blockchain over the requested timespan, optionally smoothed by a rolling average window.

## Request schema (JSON Schema)

```json
{
 "type": "object",
 "properties": {
  "cors": {
   "type": "boolean",
   "default": false,
   "description": "Enable CORS headers"
  },
  "format": {
   "enum": [
    "json",
    "csv"
   ],
   "type": "string",
   "default": "json",
   "description": "Response format:\n- `json` — Returns structured JSON with metadata and values\n- `csv` — Returns raw CSV data with timestamp and value columns (no metadata)\n"
  },
  "sampled": {
   "type": "boolean",
   "default": true,
   "description": "Apply sampling to reduce data points"
  },
  "metadata": {
   "type": "boolean",
   "default": false,
   "description": "Include metadata in response"
  },
  "timespan": {
   "type": "string",
   "default": "1y",
   "example": "1y",
   "description": "Time period (e.g., \"24h\", \"7d\", \"1y\", \"3y\")"
  },
  "rollingAverage": {
   "type": "string",
   "default": "8h",
   "example": "8h",
   "description": "Rolling average window (e.g., \"8h\", \"24h\")"
  }
 }
}
```

## Response schema (JSON Schema)

```json
{
 "type": "json",
 "format": "application/json",
 "example": {
  "name": "Number of Unspent Transaction Outputs",
  "unit": "Number of Outputs",
  "period": "day",
  "status": "ok",
  "values": [
   {
    "x": 1704067200,
    "y": 182341567
   },
   {
    "x": 1704153600,
    "y": 182618904
   }
  ],
  "description": "The number of unspent Bitcoin transactions outputs, also known as the UTXO set size."
 }
}
```

## More

- Live health (JSON, refreshed every minute): https://www.zero.xyz/c/blockchain-info-utxo-count-chart-api-7e13328f/health.json
- [Zero catalog index](https://www.zero.xyz/llms.txt)
- [Other services from api.blockchain.info](https://www.zero.xyz/host/api.blockchain.info/llms.txt)