How do I get the number of holdings and concentration of an ETF by ISIN?

Where it is in the response

Sample for iShares Core MSCI World UCITS ETF (IE00B4L5Y983):

json
"keyFacts": { "holdings": 1253 },
"profile": { "concentration": "diversified" },
"topHoldings": [ { "name": "NVIDIA", "weight": 5.48 }, { "name": "APPLE", "weight": 5.24 } ]

Where the figure comes from

The count comes from the factsheet's key facts; concentration is derived from the top holdings' weights with a published threshold, so "concentrated" means the same for a 30-stock active fund and a thematic ETF.

The request

bash
curl -s --max-time 300 https://fundfactsapi.com/api/v1/funds/IE00B4L5Y983 \
  -H "Authorization: Bearer $FUNDFACTS_API_KEY" | jq '{holdings: .data.keyFacts.holdings, concentration: .data.profile.concentration}'

python
import os, requests
r = requests.get("https://fundfactsapi.com/api/v1/funds/IE00B4L5Y983",
                 headers={"Authorization": f"Bearer {os.environ['FUNDFACTS_API_KEY']}"}, timeout=300)
fund = r.json()
print(fund["name"], fund['data']['keyFacts']['holdings'])

javascript
const res = await fetch("https://fundfactsapi.com/api/v1/funds/IE00B4L5Y983", {
  headers: { Authorization: `Bearer ${process.env.FUNDFACTS_API_KEY}` },
  signal: AbortSignal.timeout(300_000),
});
const fund = await res.json();
console.log(fund.name, fund.data.keyFacts.holdings);

Sign up at fundfactsapi.com/signup for a key; the Free plan is 15 lookups a month with no card. Without a key, GET https://fundfactsapi.com/api/v1/demo/funds/IE00B4L5Y983 returns the same payload for funds already in the store (30 calls a minute per IP; it never loads a new fund).

Caveats

• The count includes cash and derivative lines when the fund house counts them.
• Funds of funds count the underlying funds, not their constituents; use POST /portfolio for a look-through.

Several funds at once

POST /funds with { "isins": ["…", "…"], "wait": true } returns the same payload for up to 10 ISINs per call on Starter, 50 on Pro and 200 on Scale. One request is counted per ISIN answered. X-RateLimit-Remaining on every response tells you how many are left this month; a 429 rate_limited response carries Retry-After. Search and /me are free.

A fund nobody has requested in the last 24 hours is loaded on demand from the documents the fund house publishes. That first call takes 15 seconds to about 3 minutes; set your client timeout to 300 seconds and do not fire a second request for the same ISIN while the first is running. Every later call within 24 hours returns from the store in well under a second with cached: true.

Everything else in the payload is listed in the field reference.