JavaScript Number MIN_SAFE_INTEGER Property

What You’ll Learn

Number.MIN_SAFE_INTEGER is a static data property on Number (same API as MDN Number.MIN_SAFE_INTEGER). It is the smallest integer a JavaScript Number can represent exactly — −(253 − 1) (-9007199254740991). Below it, use BigInt. This tutorial covers its value, the famous −1 === −2 trap, how it mirrors MAX_SAFE_INTEGER, five examples, and try-it labs.

Introduction

Safe integers form a symmetric window around zero. The positive edge is Number.MAX_SAFE_INTEGER; the negative edge is Number.MIN_SAFE_INTEGER — exactly -Number.MAX_SAFE_INTEGER.

Inside that window, every integer is exact and comparable. Step one past the negative bound and neighbors start collapsing — just like on the positive side.

This page is part of JavaScript Number Properties. Related tools include Number.isSafeInteger(), Number.MAX_SAFE_INTEGER, and Number.MIN_VALUE (a different concept — smallest positive Number).

Understanding the MIN_SAFE_INTEGER Property

“Safe” means the integer can be stored exactly and compared correctly. The safe range is Number.MIN_SAFE_INTEGER … Number.MAX_SAFE_INTEGER inclusive.

• It is a constant number, not a method.
• Value: -9007199254740991 (−(253 − 1)).
• Equals -Number.MAX_SAFE_INTEGER.
• For more-negative exact integers, prefer BigInt.

📝 Syntax

General form of the static property Number.MIN_SAFE_INTEGER:

Number.MIN_SAFE_INTEGER

Value

-9007199254740991 (−(253 − 1)).

Property attributes

Common patterns

Number.MIN_SAFE_INTEGER;                    // -9007199254740991
Number.MIN_SAFE_INTEGER === -(2 ** 53 - 1); // true
Number.MIN_SAFE_INTEGER === -Number.MAX_SAFE_INTEGER; // true

Number.isSafeInteger(Number.MIN_SAFE_INTEGER);     // true
Number.isSafeInteger(Number.MIN_SAFE_INTEGER - 1); // false

// Prefer BigInt past the safe range:
-9007199254740993n;  // exact

Examples Gallery

Examples follow MDN Number.MIN_SAFE_INTEGER patterns. Use View Output or Try It Yourself for each case.

Number.MIN_SAFE_INTEGER;
// -9007199254740991

-9007199254740991

const x = Number.MIN_SAFE_INTEGER - 1;
const y = Number.MIN_SAFE_INTEGER - 2;

Number.MIN_SAFE_INTEGER;  // -9007199254740991
x;                        // -9007199254740992
x === y;                  // true  (!)

-9007199254740991
-9007199254740992
true

Number.isSafeInteger(Number.MIN_SAFE_INTEGER);     // true
Number.isSafeInteger(Number.MIN_SAFE_INTEGER - 1); // false

true
false

Number.MIN_SAFE_INTEGER === -Number.MAX_SAFE_INTEGER;  // true
Number.MAX_SAFE_INTEGER;  //  9007199254740991
Number.MIN_SAFE_INTEGER;  // -9007199254740991

true
9007199254740991
-9007199254740991

Number.MIN_SAFE_INTEGER;  // -9007199254740991  (exact int floor)
Number.MIN_VALUE;         // 5e-324             (tiny positive)
Number.MIN_SAFE_INTEGER < 0;  // true
Number.MIN_VALUE > 0;         // true

-9007199254740991
5e-324
true
true

🚀 Common Use Cases

• Range clamps — keep counters between MIN and MAX safe integers.
• Validation — Number.isSafeInteger(n) before trusting integer math.
• JSON numbers — stay inside the safe window or use strings / BigInt.
• Teaching floats — show the negative twin of the +1 === +2 trap.
• Not MIN_VALUE — do not use this when you mean the tiniest positive Number.
• Not -MAX_VALUE — magnitude floor for floats is different from exact-int floor.

📝 Notes

• This is a static property — use Number.MIN_SAFE_INTEGER only.
• Do not write Number.MIN_SAFE_INTEGER() — it is not a function.
• Equals -Number.MAX_SAFE_INTEGER.
• Do not confuse with Number.MIN_VALUE.
• Do not confuse with -Number.MAX_VALUE (magnitude, not exact ints).
• For more-negative exact integers, use BigInt.

💡 Best Practices