Signal8 vs OpenInsider: A Free Form 4 Screener or Insider Trades in Context

Every OpenInsider cell comes from openinsider.com, checked on 2026-11-02.

Both read the same SEC filings. A company insider who buys or sells has to file a Form 4, usually within two business days, and both sites turn those filings into tables.

OpenInsider is a screener first. It loads without an account and puts more than a dozen filters on one form: filing and trade dates, the delay between them, transaction codes, trade size, change in ownership, industry and insider title. Its ready-made lists (cluster buys, penny stock buys, CEO and CFO purchases over $25,000) cover the most common searches in one click.

Signal8 is a research site where insider trades are one layer. It follows an insider with alerts, groups cluster buys, and puts each trade next to the company's filings, dilution data and other holders.

If you want to slice every Form 4 by a precise set of conditions, OpenInsider does that for free. If you want to be told when a specific insider files, or see the filing in context, that is Signal8's side.

The home page is the screener and a set of lists. The lists are titled Latest Cluster Buys, Latest Penny Stock Buys, Latest Insider Purchases $25k+, Latest Officer Purchases $25k+, Latest CEO/CFO Purchases $25k+, the matching sales lists at $100k+, and top officer and insider purchases and sales for the day, week and month. There is also a charts page.

The screener filters on ticker, insider, share price, liquidity, filing date, trade date, filing delay, each Form 4 transaction code (purchase, sale, grant, gift, tax, option exercise and others), traded value, ownership change, industry and insider title, with grouping and sorting.

We found no pricing, account, alert or export option on its site on 2026-11-02. Its footer says the data comes from sec.gov between 6:00 and 22:00 ET on weekdays, except federal holidays.

The insiders page lists Form 3, 4 and 5 filers with full transaction histories, a 90-day cluster buying panel with the number of distinct insiders behind each one, the most active insiders, and a recent transactions table. Logged out, the shares, price and value cells stay blank; a free account fills them in.

Add an insider to a watchlist and Signal8 alerts you when they buy, sell or file any Form 3, 4 or 5. From any trade, the company page is a click away, with its SEC filings, dilution snapshot, institutional holders and congressional trades. Pro adds the API and an MCP server whose tools cover Form 4 buys and sells, cluster-buy detection and cross-company insider patterns.

• No multi-field insider screener. OpenInsider filters every Form 4 on filing delay, transaction code, trade value, ownership change, industry and title at once. Signal8's insider tables offer far fewer filters.
• Fewer ready-made lists. Signal8 has cluster buys and most active insiders; OpenInsider adds penny stock buys, CEO and CFO purchases and day, week and month leaderboards.
• Value columns need a sign-in. OpenInsider shows everything without an account.
• The API needs Pro. Signal8's API and MCP server come with the $59 plan only.

• No alerts listed. We found no way to be notified of a new filing on its site as of 2026-11-02.
• Form 4 focus. Its screener is titled a Form 4 screener, and we found no Form 3 or 5 coverage described on its site; Signal8 also covers Forms 3 and 5.
• No company context beyond the insider tables: no filings, dilution or ownership data on the pages we read.

OpenInsider fits if you want free, no-login screening of every Form 4, cut by trade size, code, delay or title, or a quick look at the day's largest officer purchases.

Signal8 fits if you follow specific insiders and want an alert when they file, or you want each trade beside the company's filings and dilution data, or in an AI assistant through MCP.

The Academy guides on Form 4 transaction codes and Form 4 vs Form 144 explain what each code means and how a planned Rule 144 sale shows up before the trade.