How to fix Error: The encoding 'utf-16' is not supported (unsupported encoding) in Node.js

Node.jsBEGINNERMEDIUMUpdated Dec 9, 2025· 160 views

This error occurs when you specify a character encoding that Node.js does not natively support, such as "utf-16" or a misspelled encoding name. Node.js supports specific encodings like utf8, utf16le, ascii, and base64.

Quick fix

Fixes ERR_UNKNOWN_ENCODING

// Wrong - will throw unsupported encoding error
const buffer = Buffer.from('Hello', 'utf-16');

// Correct - use utf16le instead
const buffer = Buffer.from('Hello', 'utf16le');

// Also valid - ucs2 is an alias for utf16le
const buffer = Buffer.from('Hello', 'ucs2');
  1. Use the correct encoding name for UTF-16
  2. Verify you are using a supported encoding
  3. Install iconv-lite for additional encodings
  4. Fix encoding parameter typos
node.js — error
// Wrong - will throw unsupported encoding error
const buffer = Buffer.from('Hello', 'utf-16');
// Correct - use utf16le instead
const buffer = Buffer.from('Hello', 'utf16le');
// Also valid - ucs2 is an alias for utf16le
const buffer = Buffer.from('Hello', 'ucs2');
Error: The encoding 'utf-16' is not supported (unsupported encoding)

What this error means

The "unsupported encoding" error is thrown when Node.js encounters a character encoding it doesn't recognize or support. This typically happens when using Buffer methods, fs operations, or stream encoding with an invalid encoding parameter. Node.js has a fixed set of supported encodings: utf8 (the default), ascii, utf16le (also called ucs2), base64, latin1 (binary), and hex. Importantly, Node.js does NOT support "utf-16" - it requires the specific variant "utf16le" (UTF-16 Little Endian). The error can also occur from simple typos like "UTF-8" (uppercase) instead of "utf8", though Node.js is usually case-insensitive for well-known encodings. This is a common issue when working with international text, file I/O, or when migrating code from other platforms that use different encoding names. Understanding which encodings Node.js supports and how to convert between them is essential for text processing applications.

Typical symptoms

  • Error message explicitly states 'encoding X is not supported'
  • Buffer.from() or fs.readFile() operations fail with encoding parameter
  • Stream operations throw error when setting encoding
  • Text appears garbled or cannot be decoded properly
  • Error occurs when working with files from external sources

Common causes

  1. Using 'utf-16' instead of the correct 'utf16le' encoding name
  2. Misspelling an encoding name (e.g., 'utf-8' might need to be 'utf8')
  3. Attempting to use an encoding not natively supported by Node.js
  4. Copying encoding names from other platforms without verifying Node.js compatibility
  5. Using uppercase encoding names when lowercase is required
  6. Trying to use specialized encodings like 'utf-16be', 'shift-jis', or 'iso-8859-2' without a conversion library

How to fix "Error: The encoding 'utf-16' is not supported (unsupported encoding)"

1Use the correct encoding name for UTF-16

Node.js does not support "utf-16" as an encoding name. Instead, use "utf16le" (UTF-16 Little Endian):

javascript
// Wrong - will throw unsupported encoding error
const buffer = Buffer.from('Hello', 'utf-16');

// Correct - use utf16le instead
const buffer = Buffer.from('Hello', 'utf16le');

// Also valid - ucs2 is an alias for utf16le
const buffer = Buffer.from('Hello', 'ucs2');

UTF-16LE is the most commonly used UTF-16 variant and works for most use cases. If you specifically need Big Endian (utf16be), you'll need a third-party library.

2Verify you are using a supported encoding

Node.js natively supports only these encodings:

javascript
// Supported encodings in Node.js:
'utf8'      // UTF-8 (default, recommended for most text)
'utf16le'   // UTF-16 Little Endian
'ucs2'      // Alias for utf16le
'ascii'     // 7-bit ASCII
'latin1'    // ISO-8859-1 / Latin-1
'binary'    // Alias for latin1
'base64'    // Base64 encoding
'hex'       // Hexadecimal encoding

Check your code for any encoding parameters and ensure they match one of these exact strings (lowercase is standard):

javascript
// Examples of correct usage
fs.readFileSync('file.txt', 'utf8');
buffer.toString('base64');
stream.setEncoding('utf8');
3Install iconv-lite for additional encodings

If you need to work with encodings not natively supported by Node.js (like utf-16be, shift-jis, gb2312, windows-1252), install the iconv-lite package:

bash
npm install iconv-lite

Then use it to convert between encodings:

javascript
const iconv = require('iconv-lite');

// Encode to UTF-16 Big Endian
const encoded = iconv.encode('Hello World', 'utf16-be');

// Decode from Shift-JIS
const decoded = iconv.decode(buffer, 'shift-jis');

// Convert file encoding
const fs = require('fs');
const fileBuffer = fs.readFileSync('file.txt');
const text = iconv.decode(fileBuffer, 'windows-1252');

iconv-lite supports over 100 encodings and is widely used in production applications, including Express.js.

4Fix encoding parameter typos

Check for common typos in encoding names:

javascript
// Common mistakes:
'UTF-8'     // Should be: 'utf8' (no dash, lowercase)
'UTF8'      // Should be: 'utf8' (lowercase)
'utf-16'    // Should be: 'utf16le'
'Unicode'   // Should be: 'utf8' or 'utf16le'
'ASCII'     // Should be: 'ascii' (lowercase)

// Correct usage:
fs.readFileSync('file.txt', 'utf8');
buffer.toString('ascii');

While Node.js is often case-insensitive for well-known encodings, it's best practice to use lowercase to avoid issues.

5Handle encoding conversion for file operations

When reading files with specific encodings, detect or specify the correct encoding:

javascript
const fs = require('fs');
const iconv = require('iconv-lite');

// For files with known non-UTF-8 encoding
const fileBuffer = fs.readFileSync('data.txt');
const text = iconv.decode(fileBuffer, 'windows-1252');

// For writing with specific encoding
const content = 'Hello World';
const encoded = iconv.encode(content, 'utf16-le');
fs.writeFileSync('output.txt', encoded);

If the file encoding is unknown, consider using a library like chardet to detect it automatically.

Advanced notes

UTF-16 variants: Node.js only supports UTF-16LE natively because it's the most common variant used by Windows and JavaScript's internal string representation. If you need UTF-16BE (Big Endian) or UTF-16 with BOM (Byte Order Mark), you must use iconv-lite or another encoding library.

Performance considerations: Native Node.js encodings (utf8, ascii, utf16le) are implemented in C++ and are significantly faster than third-party JavaScript implementations. Use native encodings whenever possible for performance-critical applications.

Buffer vs String encoding: When using Buffer.from(string, encoding), the encoding parameter specifies how to interpret the string. When using buffer.toString(encoding), it specifies how to decode the buffer. These are inverse operations.

Stream encoding: When setting encoding on readable streams with stream.setEncoding(encoding), only the six core encodings are supported. For other encodings, pipe the stream through iconv-lite's decodeStream().

International text: UTF-8 is the recommended encoding for international text and is the default in Node.js. It's compatible with ASCII and uses 1-4 bytes per character, making it efficient for most languages. Only use other encodings when required by external systems or legacy file formats.

Frequently asked questions

What does "ERR_UNKNOWN_ENCODING" mean?
js encounters a character encoding it doesn't recognize or support. This typically happens when using Buffer methods, fs operations, or stream encoding with an invalid encoding parameter. js has a fixed set of supported encodings: utf8 (the default), ascii, utf16le (also called ucs2), base64, latin1 (binary), and hex.
How do I fix "ERR_UNKNOWN_ENCODING"?
This error occurs when you specify a character encoding that Node.js does not natively support, such as "utf-16" or a misspelled encoding name. Node.js supports specific encodings like utf8, utf16le, ascii, and base64.
What causes "ERR_UNKNOWN_ENCODING"?
Using 'utf-16' instead of the correct 'utf16le' encoding name Misspelling an encoding name (e.g., 'utf-8' might need to be 'utf8') Attempting to use an encoding not natively supported by Node.js
Is the "ERR_UNKNOWN_ENCODING" error serious?
It is a medium-severity error — more of a blocker than a risk. The steps above resolve it.

Official resources & further reading