Baseline Widely available

This feature is well established and works across many devices and browser versions. It’s been available across browsers since September 2020.

The toString() method of BigInt values returns a string representing the specified BigInt value. The trailing "n" is not part of the string.

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radix Optional

An integer in the range 2 through 36 specifying the base to use for representing the BigInt value. Defaults to 10.

Return value

A string representing the specified BigInt value.



Thrown if radix is less than 2 or greater than 36.


The BigInt object overrides the toString method of Object; it does not inherit Object.prototype.toString(). For BigInt values, the toString() method returns a string representation of the value in the specified radix.

For radixes above 10, the letters of the alphabet indicate digits greater than 9. For example, for hexadecimal numbers (base 16) a through f are used.

If the specified BigInt value is negative, the sign is preserved. This is the case even if the radix is 2; the string returned is the positive binary representation of the BigInt value preceded by a - sign, not the two's complement of the BigInt value.

The toString() method requires its this value to be a BigInt primitive or wrapper object. It throws a TypeError for other this values without attempting to coerce them to BigInt values.

Because BigInt doesn't have a [@@toPrimitive]() method, JavaScript calls the toString() method automatically when a BigInt object is used in a context expecting a string, such as in a template literal. However, BigInt primitive values do not consult the toString() method to be coerced to strings — rather, they are directly converted using the same algorithm as the initial toString() implementation.

BigInt.prototype.toString = () => "Overridden";
console.log(`${1n}`); // "1"
console.log(`${Object(1n)}`); // "Overridden"


Using toString()

17n.toString(); // "17"
66n.toString(2); // "1000010"
254n.toString(16); // "fe"
(-10n).toString(2); // "-1010"
(-0xffn).toString(2); // "-11111111"

Negative-zero BigInt

There is no negative-zero BigInt as there are no negative zeros in integers. -0.0 is an IEEE floating-point concept that only appears in the JavaScript Number type.

(-0n).toString(); // "0"
BigInt(-0).toString(); // "0"


ECMAScript Language Specification
# sec-bigint.prototype.tostring

Browser compatibility

BCD tables only load in the browser

See also