Mempool API

⭐ Beginner's Pick Cryptocurrency / No Auth Required Beginner HTTPS
Free to Use Varies (check documentation)

Overview

Mempool.space is a Bitcoin blockchain explorer API that focuses on real-time transaction fee estimation and mempool (pending transaction pool) analytics. It provides recommended fee rates in sat/vByte so developers can help users set appropriate transaction fees for timely confirmation. No API key or authentication is needed, making it one of the most accessible Bitcoin APIs for beginners.

💡

Beginner Tip

Use the /api/v1/fees/recommended endpoint to instantly get the current Bitcoin fee recommendation — no sign-up required, just call the URL and use the "fastestFee" value to set an appropriate fee for urgent transactions.

Available Data

coin price in USD/EUR
market capitalization
24h price change
trading volume
circulating supply

Example Response

JSON Response
{
  "id": "bitcoin",
  "symbol": "btc",
  "current_price": 65432.1,
  "market_cap": 1280000000000,
  "price_change_24h": 1250.5,
  "price_change_percentage_24h": 1.95,
  "total_volume": 28500000000
}

Field Reference

fastestFee Recommended fee in sat/vByte to get confirmed in the next block (~10 minutes).
halfHourFee Fee rate in sat/vByte for confirmation within approximately 30 minutes.
hourFee Fee rate in sat/vByte for confirmation within approximately 1 hour.
economyFee Lower-priority fee rate in sat/vByte; confirmation may take several hours.
minimumFee Minimum fee rate accepted by the network; transactions below this are likely rejected.

Implementation Example

// ⚠️ Note: This URL may be a documentation page. Check official docs for actual API endpoint.
const url = "https://mempool.space/api";
const response = await fetch(url);
if (!response.ok) throw new Error(`Request failed: ${response.status}`);
const data = await response.json();
console.log(data);

What Can You Build?

Note: These code examples are AI-generated and unverified. Always refer to the official API documentation for accurate usage.

Common Errors & Troubleshooting

CORS error in browser Mempool.space does not support CORS for all endpoints, blocking direct browser fetch calls.
Make requests from your backend server instead of the browser, or use the mempool.space JavaScript library which handles this.
404 Not Found for transaction ID Querying a transaction that is not yet indexed or the TX ID has a typo.
Verify the 64-character hex transaction ID is complete and correct; newly broadcast transactions may take a moment to appear.
Rate limited (HTTP 429) Sending too many requests in a short period from the same IP address.
Cache fee recommendations locally for at least 30 seconds — fees do not change that rapidly, so frequent polling is unnecessary.

Matrix Score Breakdown

🌐 Reachability 30/30
⚡ Speed 20/20
🔒 Security 15/15
🛠 Developer XP 12/20
✓ Reliability 7/15
Response Time 37ms

Fully tested on Apr 5, 2026

Technical Specifications

Auth No Auth
HTTPS REQUIRED
CORS NO
Category Cryptocurrency
Difficulty Beginner
Verified: 2026-04-07

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