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  4. Standard built-in objects
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decodeURI()

Baseline Widely available

This feature is well established and works across many devices and browser versions. It’s been available across browsers since July 2015.

The decodeURI() function decodes a Uniform Resource Identifier (URI) previously created by encodeURI() or a similar routine.

In this article

Try it

const uri = "https://mozilla.org/?x=шеллы"; const encoded = encodeURI(uri); console.log(encoded); // Expected output: "https://mozilla.org/?x=%D1%88%D0%B5%D0%BB%D0%BB%D1%8B" try { console.log(decodeURI(encoded)); // Expected output: "https://mozilla.org/?x=шеллы" } catch (e) { // Catches a malformed URI console.error(e); }

Syntax

js
decodeURI(encodedURI)

Parameters

encodedURI

A complete, encoded Uniform Resource Identifier.

Return value

A new string representing the unencoded version of the given encoded Uniform Resource Identifier (URI).

Exceptions

URIError

Thrown if encodedURI contains a % not followed by two hexadecimal digits, or if the escape sequence does not encode a valid UTF-8 character.

Description

decodeURI() is a function property of the global object.

The decodeURI() function decodes the URI by treating each escape sequence in the form %XX as one UTF-8 code unit (one byte). In UTF-8, the number of leading 1 bits in the first byte, which may be 0 (for 1-byte ASCII characters), 2, 3, or 4, indicates the number of bytes in the character. So by reading the first escape sequence, decodeURI() can determine how many more escape sequences to consume. If decodeURI() fails to find the expected number of sequences, or if the escape sequences don't encode a valid UTF-8 character, a URIError is thrown.

decodeURI() decodes all escape sequences, but if the escape sequence encodes one of the following characters, the escape sequence is preserved in the output string (because they are part of the URI syntax):

; / ? : @ & = + $ , #

Examples

Decoding a Cyrillic URL

js
decodeURI( "https://developer.mozilla.org/ru/docs/JavaScript_%D1%88%D0%B5%D0%BB%D0%BB%D1%8B", ); // "https://developer.mozilla.org/ru/docs/JavaScript_шеллы"

decodeURI() vs. decodeURIComponent()

decodeURI() assumes the input is a full URI, so it does not decode characters that are part of the URI syntax.

js
decodeURI( "https://developer.mozilla.org/docs/JavaScript%3A%20a_scripting_language", ); // "https://developer.mozilla.org/docs/JavaScript%3A a_scripting_language" decodeURIComponent( "https://developer.mozilla.org/docs/JavaScript%3A%20a_scripting_language", ); // "https://developer.mozilla.org/docs/JavaScript: a_scripting_language"

Catching errors

js
try { const a = decodeURI("%E0%A4%A"); } catch (e) { console.error(e); } // URIError: malformed URI sequence

Specifications

Specification
ECMAScript® 2027 Language Specification
# sec-decodeuri-encodeduri

Browser compatibility

Enable JavaScript to view this browser compatibility table.

See also

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  1. JavaScript
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  3. JavaScript Guide
    1. Introduction
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    6. Expressions and operators
    7. Numbers and strings
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    12. Working with objects
    13. Using classes
    14. Using promises
    15. JavaScript typed arrays
    16. Iterators and generators
    17. Resource management
    18. Internationalization
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  4. Intermediate
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  5. Advanced
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  6. References
  7. Built-in objects
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    10. BigInt
    11. BigInt64Array
    12. BigUint64Array
    13. Boolean
    14. DataView
    15. Date
    16. decodeURI()
    17. decodeURIComponent()
    18. DisposableStack
    19. encodeURI()
    20. encodeURIComponent()
    21. Error
    22. escape()
    23. eval()
    24. EvalError
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  8. Expressions & operators
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    51. SyntaxError: invalid named capture reference in regular expression
    52. SyntaxError: invalid property name in regular expression
    53. SyntaxError: invalid range in character class
    54. SyntaxError: invalid regexp group
    55. SyntaxError: invalid regular expression flag "x"
    56. SyntaxError: invalid unicode escape in regular expression
    57. SyntaxError: JSON.parse: bad parsing
    58. SyntaxError: label not found
    59. SyntaxError: missing : after property id
    60. SyntaxError: missing ) after argument list
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    62. SyntaxError: missing ] after element list
    63. SyntaxError: missing } after function body
    64. SyntaxError: missing } after property list
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    66. SyntaxError: missing formal parameter
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    71. SyntaxError: nothing to repeat
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    73. SyntaxError: octal escape sequences can't be used in untagged template literals or in strict mode code
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    91. SyntaxError: Using //@ to indicate sourceURL pragmas is deprecated. Use //# instead
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    97. TypeError: "x" is not a non-null object
    98. TypeError: "x" is read-only
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    104. TypeError: can't convert BigInt to number
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    106. TypeError: can't define property "x": "obj" is not extensible
    107. TypeError: can't delete non-configurable array element
    108. TypeError: can't redefine non-configurable property "x"
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    110. TypeError: can't set prototype: it would cause a prototype chain cycle
    111. TypeError: cannot use 'in' operator to search for 'x' in 'y'
    112. TypeError: class constructors must be invoked with 'new'
    113. TypeError: cyclic object value
    114. TypeError: derived class constructor returned invalid value x
    115. TypeError: getting private setter-only property
    116. TypeError: Initializing an object twice is an error with private fields/methods
    117. TypeError: invalid 'instanceof' operand 'x'
    118. TypeError: invalid Array.prototype.sort argument
    119. TypeError: invalid assignment to const "x"
    120. TypeError: Iterator/AsyncIterator constructor can't be used directly
    121. TypeError: matchAll/replaceAll must be called with a global RegExp
    122. TypeError: More arguments needed
    123. TypeError: null/undefined has no properties
    124. TypeError: property "x" is non-configurable and can't be deleted
    125. TypeError: Reduce of empty array with no initial value
    126. TypeError: setting getter-only property "x"
    127. TypeError: WeakSet key/WeakMap value 'x' must be an object or an unregistered symbol
    128. TypeError: X.prototype.y called on incompatible type
    129. URIError: malformed URI sequence
    130. Warning: -file- is being assigned a //# sourceMappingURL, but already has one
    131. Warning: unreachable code after return statement
  14. Misc
    1. JavaScript technologies overview
    2. Execution model
    3. Lexical grammar
    4. Iteration protocols
    5. Strict mode
    6. Template literals
    7. Trailing commas
    8. Deprecated features

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