Free, instant signup at finnhub.io/register. This is the primary data source — no key means the page falls back to slower, less reliable public proxies for everything.
Free tier is only 800 credits/month — at 66 tickers that's burned in about 12 refreshes. This is now the last fallback (after Finnhub and Yahoo), only called if both of those miss a symbol. Leave blank if you'd rather it just show stale/cached data than spend credits.