Most significant bits

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The terms “most significant bit” (MSB) and “least significant bit” (LSB) describe the relative importance of each bit in a binary number based on how much it affects the overall value. The most significant bit is the leftmost bit and represents the highest place value (such as 2⁷ = 128 in an 8-bit number), while the least significant bit is the rightmost bit and represents the smallest place value (2^0 = 1). 

This naming reflects their impact: changing the MSB causes a large shift in value, whereas changing the LSB only alters the value slightly.

For example, flipping the MSB in the binary number 10000000 to 00000000 drops the decimal value from 128 to 0—a significant change. In contrast, flipping the LSB in 10000000 to 10000001 increases the value from 128 to 129—only a minor change. Thus, the MSB is the most impactful in determining a number’s magnitude, and the LSB is the least.