Insiders Trades Sigma vs OpenInsider
For twenty years, OpenInsider has been the free go-to for US insider buys. It does one thing well: surface SEC Form 4 filings in a readable table. But it stops there, no Europe, no API, no scoring, no backtest, no AI agents. Sigma keeps OpenInsider's open spirit and pushes it into 2026: five regulated markets unified (AMF, SEC, BaFin, SIX SER, RNS), FX normalisation, open-formula composite score, free historical backtest, REST API, and an MCP server.
Market coverage
OpenInsider is strictly limited to SEC territory: US tickers, Form 4. If an LVMH director files a €12M buy, it never shows. Sigma aggregates the equivalent filings in France (AMF BDIF), Germany (BaFin DDA), Switzerland (SIX SER) and the UK (RNS via Investegate), with a common role mapping (CEO/Vorstand/PDG/CFO…) and instrument mapping (shares, options, ADRs). One API call, five regulators.
Scoring and backtest
OpenInsider sorts by buy size or frequency, useful, but raw. Sigma computes a 100-point composite score (size relative to market cap, insider's historical conviction, role, sector momentum) whose formula is fully public on /methodologie. More importantly, every score is validated by a 2020–2026 historical backtest whose results (win rate, T+30/90/365 returns, Sharpe, alpha vs local benchmark) are accessible for free in the viewer. You don't just see which insiders bought, you see what happened the last time a similar signal fired.
API and MCP: what OpenInsider doesn't have
OpenInsider has no official API. Community scrapers exist but they're brittle. Sigma exposes a documented REST API (Free: account required, 15 pages/day, web only · Pro at €19/mo: 10k requests, MCP, 5-year history, 1 webhook · Quant at €99/mo: 100k requests, unlimited webhooks, bulk exports, 5 seats), with a stable JSON schema, plus an MCP server that lets Claude, ChatGPT or Cursor query the database directly. Ask your AI agent: "Which Allianz directors bought over €100k in the past 30 days?", the tool call returns a structured answer, no scraping, no aggressive rate limiting.
When to prefer OpenInsider
Honestly: if you trade only US small-caps, don't use AI agents, don't need European coverage, and don't want to spend a euro, OpenInsider stays perfect. It exists, it works, it's legendary. Sigma fits the next case: you also track SBF 120, DAX, SMI, FTSE, you want a backtested reproducible score, and/or you're building a product (bot, dashboard, AI agent) that needs a stable API.
One-line verdict
OpenInsider is the open US archive; Sigma is the multi-market, scored, backtested, API-first platform OpenInsider could have become if it had launched in 2026.