CoinGecko API: Build a Free Crypto Portfolio Tracker in Python (No API Key Required)

#api #crypto #python #tutorial

I watched a friend pay $30/month for CoinMarketCap Pro to track his crypto portfolio. I built the same thing in 30 minutes — for free, with no API key.

CoinGecko has the most generous free API in crypto. Here's how to use it.

Why CoinGecko API?

No API key needed for basic endpoints (just make HTTP requests)
13,000+ cryptocurrencies tracked
Exchange data from 800+ exchanges
Historical data going back years
NFT data included
Rate limit: 10-30 requests/minute (free)

Step 1: Get Current Prices (No Key Needed!)

import requests

def get_crypto_prices(coins, currency="usd"):
    """Get current prices for multiple cryptocurrencies."""
    url = "https://api.coingecko.com/api/v3/simple/price"
    params = {
        "ids": ",".join(coins),
        "vs_currencies": currency,
        "include_24hr_change": "true",
        "include_market_cap": "true",
    }
    return requests.get(url, params=params).json()

# Get prices for top cryptos
prices = get_crypto_prices(["bitcoin", "ethereum", "solana", "cardano"])
for coin, data in prices.items():
    price = data["usd"]
    change = data["usd_24h_change"]
    emoji = "📈" if change > 0 else "📉"
    print(f"{emoji} {coin.title()}: ${price:,.2f} ({change:+.1f}%)")

Output:

📈 Bitcoin: $67,234.00 (+2.3%)
📉 Ethereum: $3,456.78 (-1.2%)
📈 Solana: $178.90 (+5.4%)
📉 Cardano: $0.45 (-0.8%)

Step 2: Portfolio Tracker

# Your portfolio
PORTFOLIO = {
    "bitcoin": 0.5,      # 0.5 BTC
    "ethereum": 3.0,      # 3 ETH
    "solana": 25.0,       # 25 SOL
    "cardano": 5000.0,    # 5000 ADA
}

def portfolio_value():
    """Calculate total portfolio value."""
    coins = list(PORTFOLIO.keys())
    prices = get_crypto_prices(coins)

    total = 0
    print(f"\n{Coin:<12} {Amount:>10} {Price:>12} {Value:>12} {24h:>8}")
    print("-" * 58)

    for coin, amount in PORTFOLIO.items():
        price = prices[coin]["usd"]
        value = price * amount
        change = prices[coin]["usd_24h_change"]
        total += value

        print(f"{coin.title():<12} {amount:>10.2f} ${price:>10,.2f} ${value:>10,.2f} {change:>+7.1f}%")

    print("-" * 58)
    print(f"{TOTAL:<12} {:>10} {:>12} ${total:>10,.2f}")
    return total

portfolio_value()

Step 3: Historical Data & Charts

import matplotlib.pyplot as plt
from datetime import datetime

def get_price_history(coin_id, days=30):
    """Get historical prices."""
    url = f"https://api.coingecko.com/api/v3/coins/{coin_id}/market_chart"
    params = {"vs_currency": "usd", "days": days}
    data = requests.get(url, params=params).json()

    prices = data["prices"]  # [[timestamp, price], ...]
    dates = [datetime.fromtimestamp(p[0]/1000) for p in prices]
    values = [p[1] for p in prices]
    return dates, values

# Compare BTC vs ETH (normalized)
fig, ax = plt.subplots(figsize=(12, 6))
for coin in ["bitcoin", "ethereum", "solana"]:
    dates, values = get_price_history(coin, 90)
    normalized = [(v / values[0] - 1) * 100 for v in values]
    ax.plot(dates, normalized, label=coin.title())

ax.set_title("90-Day Crypto Performance (% Change)")
ax.set_ylabel("% Change from Start")
ax.legend()
ax.grid(True, alpha=0.3)
plt.tight_layout()
plt.savefig("crypto_comparison.png", dpi=150)

Step 4: Fear & Greed Index Alternative

def get_market_overview():
    """Build your own market sentiment indicator."""
    url = "https://api.coingecko.com/api/v3/global"
    data = requests.get(url).json()["data"]

    btc_dominance = data["market_cap_percentage"]["btc"]
    total_mcap = data["total_market_cap"]["usd"]
    mcap_change = data["market_cap_change_percentage_24h_usd"]

    # Simple sentiment based on 24h market change
    if mcap_change > 5:
        sentiment = "🟢 Extreme Greed"
    elif mcap_change > 2:
        sentiment = "🟢 Greed"
    elif mcap_change > -2:
        sentiment = "🟡 Neutral"
    elif mcap_change > -5:
        sentiment = "🔴 Fear"
    else:
        sentiment = "🔴 Extreme Fear"

    print(f"Total Crypto Market Cap: ${total_mcap/1e12:.2f}T")
    print(f"24h Change: {mcap_change:+.2f}%")
    print(f"BTC Dominance: {btc_dominance:.1f}%")
    print(f"Sentiment: {sentiment}")

get_market_overview()

Step 5: Trending Coins (What's Hot?)

def get_trending():
    """What's trending on CoinGecko right now?"""
    url = "https://api.coingecko.com/api/v3/search/trending"
    data = requests.get(url).json()

    print("🔥 Trending Coins (last 24h):")
    for item in data["coins"][:7]:
        coin = item["item"]
        print(f"  #{coin['market_cap_rank']} {coin['name']} ({coin['symbol']}) "
              f"— Score: {coin['score']}")

get_trending()

CoinGecko vs Paid Alternatives

Feature	CoinGecko (Free)	CoinMarketCap Pro ($30/mo)	Messari ($30/mo)
API Key Required	❌ No	✅ Yes	✅ Yes
Coins tracked	13,000+	9,000+	5,000+
Historical data	✅	✅	✅
NFT data	✅	❌	❌
Exchange data	800+	600+	200+
Rate limit	10-30/min	30/min	20/min
Price	$0	$30/mo	$30/mo