What is the Plugins Array?

The plugins array is the browser’s navigator.plugins collection: a list-like object of installed browser plugins, each with properties such as name, description, filename, and supported MIME types. In JavaScript it behaves like an array for length and indexing but is a PluginArray type, not a native Array.

How plugins are exposed today

Historically, sites checked for Flash or other NPAPI plugins before loading content. Modern browsers have removed most plugins; many profiles now show only built-in handlers (such as PDF) or an empty list. The API remains for compatibility.

Scripts can loop navigator.plugins and read metadata. The data is read-only; pages cannot install plugins through this API.

Because the list is small and stable on mainstream browsers, the exact combination of entries, order, and MIME data was often hashed as part of browser fingerprinting.

Why the plugins array matters for fraud and bots

Headless browsers, automation kits, and some privacy browsers present plugin sets that differ from typical consumer Chrome, Edge, or Safari. Attackers may copy a user agent but forget to align plugins, MIME lists, or version strings. Mass traffic from one toolkit can produce identical or nearly identical plugin fingerprints across many IPs.

Anti-fraud systems compare plugin signals to other attributes (OS claim, WebGL, fonts, canvas) and to behavior. Mismatches and clones support scores for bots, proxy abuse, and click fraud. Empty lists are not proof of fraud (privacy-focused users may hide plugins), so vendors combine this with broader detection and patterns tied to ad fraud. Technical context appears in device spoofing and bot detection techniques.