This new major version of Node.js delivers significant improvements in performance, reliability, usability and security. Module loading is nearly four times faster than in Node.js v4, tests and documentation have seen significant improvements, usability of the Buffer and File System APIs have been improved, and Node.js now supports 93% of ES6 language features, thanks to V8 version 5.0.

The following significant changes have been made since the previous Node.js v5.0.0 release.

• Buffer
  • New Buffer constructors have been added #4682 and #5833.
  • Existing Buffer() and SlowBuffer() constructors have been deprecated in docs #4682 and #5833.
  • Previously deprecated Buffer APIs are removed #5048, #4594.
  • Improved error handling #4514.
  • The Buffer.prototype.lastIndexOf() method has been added #4846.
• Cluster
  • Worker emitted as first argument in ‘message’ event #5361.
  • The worker.exitedAfterDisconnect property replaces worker.suicide #3743.
• Console
  • Calling console.timeEnd() with an unknown label now emits a process warning rather than throwing#5901.
• Crypto
  • Improved error handling #3100, #5611.
  • Simplified Certificate class bindings #5382.
  • Improved control over FIPS mode #5181.
  • pbkdf2 digest overloading is deprecated #4047.
• Dependencies
  • Reintroduce shared c-ares build support #5775.
  • V8 updated to 5.0.71.35 #6372.
• DNS
  • Add dns.resolvePtr() API to query plain DNS PTR records #4921.
• Domains
  • Clear stack when no error handler #4659.
• Events
  • The EventEmitter.prototype._events object no longer inherits from Object.prototype #6092.
  • The EventEmitter.prototype.prependListener() and EventEmitter.prototype.prependOnceListener()methods have been added #6032.
• File System
  • The fs.realpath() and fs.realpathSync() methods have been updated to use a more efficient libuv-based implementation. This change includes the removal of the cache argument and the method can throw new errors #3594.
  • FS apis can now accept and return paths as Buffers #5616.
  • Error handling and type checking improvements #5616, #5590, #4518, #3917.
  • fs.read’s string interface is deprecated #4525.
• HTTP
  • ‘clientError’ can now be used to return custom errors from an HTTP server #4557.
• Modules
  • Current directory is now prioritized for local lookups #5689.
  • Symbolic links are preserved when requiring modules #5950.
• Net
  • DNS hints no longer implicitly set #6021.
  • Improved error handling and type checking #5981, #5733, #2904.
• OS X
  • MACOSX_DEPLOYMENT_TARGET has been bumped up to 10.7 #6402.
• Path
  • Improved type checking #5348.
• Process
  • Introduce process warnings API #4782.
  • Throw exception when non-function passed to nextTick #3860.
• Querystring
  • The object returned by querystring.parse() no longer inherits from Object.prototype #6055.
• Readline
  • Key info is emitted unconditionally #6024.
  • History can now be explicitly disabled #6352.
• REPL
  • Assignment to _ will emit a warning #5535.
  • Expressions will no longer be completed when eval fails #6328.
• Timers
  • Fail early when callback is not a function #4362.
• Streams
  • null is now an invalid chunk to write in object mode #6170.
• TLS
  • Rename ‘clientError’ to ‘tlsClientError’ #4557.
  • SHA1 used for sessionIdContext #3866.
• TTY
  • Previously deprecated setRawMode wrapper is removed #2528.
• URL
  • Username and password will be dropped by url.resolve() if the host changes #1480.
• Util
  • Changes to Error object formatting #4582.
  • The util._extend() method has been deprecated #4903
  • The util.log() method has been deprecated #6161.
• Windows
  • Windows XP and Vista are no longer supported #5167.
• Zlib
  • Multiple improvements have been made to Zlib processing #5883 and #5707.