__proto__Limited availability
The __proto__ property of objects partially exposes the prototype of an object.
Not yet supported in all major browsers — check the table and provide a fallback.
Discouraged: Changing __proto__ is slow and can cause surprising bugs.
Browser support
DesktopChrome
1+Supportedsince Dec 11, 2008
Current: 155Edge
12+Supportedsince Jul 29, 2015
Current: 154Firefox
1+Supportedsince Nov 9, 2004
Current: 157Safari
1–2Not supported
3+Supportedsince Oct 26, 2007
Current: 27MobileChrome Android
18+Supportedsince Jun 27, 2012
Current: 155Firefox Android
4+Supportedsince Mar 29, 2011
Current: 157Safari iOS
1+Supportedsince Jun 29, 2007
Current: 27How to use
Support is still inconsistent across browsers. Use feature detection and test carefully.
Example
Full syntax and examples are on MDN: proto.
Feature detection
JS · check before using
if ("proto" in Object || ("prototype" in Object && "proto" in Object.prototype)) {
// Object.proto is available
}