Hermes plans to target ECMAScript 2015 (ES6), with some carefully considered exceptions.

• Symbols (including most well-known Symbols)
• Iteration (with [Symbol.iterator])
• for..of loops
• Destructuring assignment (with array and object "rest" properties)
• Template string literals
• Generators (function* and yield)
• TypedArrays
• Arrow functions
• All ES6 JS library functions
  • Set/Map
  • WeakSet/WeakMap
  • ES6 String searching functions
  • ES6 Array searching functions

• let and const (block scoped variables, with support for the temporal dead zone)
• Classes and method definitions
• Computed property keys on object literals
• ES modules (import and export)
• Intl API glue for Android has been added, in order to enable community contribution of a complete, spec-compliant implementation.
• Reflection (Reflect and Proxy) is opt-in until it is stablilized.

• Realms
• with statements
• Local mode eval() (use and introduce local variables)
• Symbol.species and its interactions with JS library functions
• use of constructor property when creating new Arrays in Array.prototype methods
• Symbol.unscopables (Hermes does not support with)
• Other features added to ECMAScript after ES6 not listed under "Supported"

• Function.prototype.toString cannot show source because Hermes executes from bytecode
• arguments changes in non-strict mode will not sync with named parameters