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The Number.isSafeInteger() method determines whether the provided value is a number that is a safe integer.

A safe integer is an integer that

  • can be exactly represented as an IEEE-754 double precision number, and
  • whose IEEE-754 representation cannot be the result of rounding any other integer to fit the IEEE-754 representation.

For example, 253 - 1 is a safe integer: it can be exactly represented, and no other integer rounds to it under any IEEE-754 rounding mode. In contrast, 253 is not a safe integer: it can be exactly represented in IEEE-754, but the integer 253 + 1 can't be directly represented in IEEE-754 but instead rounds to 253 under round-to-nearest and round-to-zero rounding.  The safe integers consist of all integers from -(253 - 1) inclusive to 253 - 1 inclusive (± 9007199254740991 or ± 9,007,199,254,740,991).  

Handling values larger or smalller than ~9 quadrillion with full precision requires using an arbitrary precision arithmetic library.  See What Every Programmer Needs to Know about Floating Point Arithmetic for more information on floating point representations of numbers.




The value to be tested for being a safe integer.

Return value

A Boolean indicating whether or not the given value is a number that is a safe integer.


Number.isSafeInteger(3);                    // true
Number.isSafeInteger(Math.pow(2, 53));      // false
Number.isSafeInteger(Math.pow(2, 53) - 1);  // true
Number.isSafeInteger(NaN);                  // false
Number.isSafeInteger(Infinity);             // false
Number.isSafeInteger('3');                  // false
Number.isSafeInteger(3.1);                  // false
Number.isSafeInteger(3.0);                  // true


Number.isSafeInteger = Number.isSafeInteger || function (value) {
   return Number.isInteger(value) && Math.abs(value) <= Number.MAX_SAFE_INTEGER;


Specification Status Comment
ECMAScript 2015 (6th Edition, ECMA-262)
The definition of 'Number.isSafeInteger' in that specification.
Standard Initial definition.
ECMAScript Latest Draft (ECMA-262)
The definition of 'Number.isSafeInteger' in that specification.

Browser compatibility

FeatureChromeEdgeFirefoxInternet ExplorerOperaSafari
Basic support Yes Yes32 No Yes10
FeatureAndroid webviewChrome for AndroidEdge mobileFirefox for AndroidOpera AndroidiOS SafariSamsung Internet
Basic support Yes Yes Yes32 Yes Yes Yes

See also

Document Tags and Contributors

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