IG vs Portfolio Optimizer

IG's trading API layers REST order execution and Lightstreamer-based streaming onto the same CFD, spread-betting, and forex engine behind IG's own platform, authenticated with an API key generated from a live account (a linked demo account then lets you sandbox trades risk-free). There's no separate API fee — access is included with any account and gated only by IG's standard per-key usage quotas, not a metered price. A live probe of the real API host (api.ig.com) returned `Access-Control-Allow-Origin: *` even on an error response, confirming CORS is open — correcting the previously-recorded `unknown`.

Portfolio Optimizer is a free, no-signup Web API implementing modern-portfolio-theory algorithms — mean-variance and minimum-variance optimization, risk and performance analytics, backtesting, and factor-model tools — over JSON, so it can be called from Python, Excel, Google Sheets, or any HTTP client without an SDK. The homepage explicitly advertises free access with no registration required, and a live test against a real optimization endpoint (api.portfoliooptimizer.io) returned `Access-Control-Allow-Origin: *` on both a route-not-found and a malformed-payload response, confirming CORS is enabled; the same responses carry a `WWW-Authenticate: Key` header hinting at an optional key for higher throughput, though the observed default rate limit is a modest 1 request/second.