# Blockchain.com Explorer API – Average Block Size Chart

> Blockchain.com Explorer API – Average Block Size Chart 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 Bitcoin average block size chart data over a configurable time period and rolling average window

## Facts

- Endpoint: POST https://api.blockchain.info/explorer-gateway-kt/x402/charts/avg-block-size?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-com-explorer-api-average-block-size-chart-4dea5d3c
- Structured record (JSON): https://api.zero.xyz/v1/capabilities/cap_smes-9QCUdHoCHUounead

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-com-explorer-api-average-block-size-chart-4dea5d3c -d '<json body>'
```

Example prompt: Pull the Blockchain.com average Bitcoin block size chart for the past year using a 24-hour rolling average and return it as JSON.

## When to prefer this

Use this endpoint when you need historical Bitcoin average block size time-series data from Blockchain.com's Explorer, especially when you need configurable time windows, rolling averages, or both JSON and CSV output formats. Prefer this over generic blockchain APIs when you specifically need block size metrics (not transaction counts, fees, or price data) and when you need fine-grained control over the rolling average window.

## Known failure modes

- Invalid timespan format returns a 400 error
- Unsupported rollingAverage value may return an error or unexpected results
- Payment not processed (402) if x402 payment header is missing or insufficient
- Rate limiting if too many requests are made in a short period
- Network timeouts for very large timespans with sampling disabled

## How this service works

Paid AI-agent access to Blockchain.com Explorer API

## Output

Returns a time-series dataset of average Bitcoin block sizes, including timestamps and values. In JSON mode, may include chart metadata such as name, description, and units. In CSV mode, returns raw two-column data (timestamp, value). The rolling average window and timespan control data granularity and coverage.

## 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": "Average Block Size",
  "unit": "MB",
  "period": "day",
  "status": "ok",
  "values": [
   {
    "x": 1704067200,
    "y": 1.62
   },
   {
    "x": 1704153600,
    "y": 1.71
   }
  ],
  "description": "The average block size in MB."
 }
}
```

## More

- Live health (JSON, refreshed every minute): https://www.zero.xyz/c/blockchain-com-explorer-api-average-block-size-chart-4dea5d3c/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)