Does my data get uploaded anywhere?
No. Everything runs locally in your browser and nothing is sent to a server.
Is this free to use?
Yes. It is completely free, with no account, no signup, and no usage limits.
Does it work on a phone?
Yes. The page runs in any modern mobile browser, on iPhone and Android alike, with no app to install.
How do I read a binary number by hand?
Label the digits from the right with 1, 2, 4, 8, 16 and so on, then add up the place values where the digit is 1. For 1010 that is 8 and 2, which gives 10. The tool does the same thing, only with arbitrary-precision arithmetic so it never overflows.
Why does 11111111 give 255 instead of -1?
Because the converter treats the input as an unsigned magnitude. Two's complement only has meaning once you fix a width, and this tool has no width. If you know the value is a signed 8-bit byte with the top bit set, subtract 256: 255 - 256 gives -1.
What is the biggest number 8, 16 and 32 bits can hold?
Unsigned, they hold 255, 65,535 and 4,294,967,295 respectively, which are 11111111, sixteen ones, and thirty-two ones. Signed, using two's complement, the ranges are -128 to 127, -32,768 to 32,767, and about plus or minus 2.15 billion.
Can I convert a binary fraction like 1010.11?
No. The parser accepts integers only, so the decimal point is reported as an invalid binary digit. Convert the integer part here and handle the fractional bits separately, where each place after the point is 0.5, 0.25, 0.125 and so on.
Does it handle 64-bit values without losing precision?
Yes. Parsing runs on arbitrary-precision integers rather than floating-point numbers, so a full 64-bit binary string converts exactly. Doing the same in a spreadsheet or with a plain JavaScript number would silently round anything above 9,007,199,254,740,991.
Can I paste several binary numbers at once?
Yes. Separate them with spaces, commas, or new lines and each is converted independently. The output keeps the same order, so a column of binary values comes back as a column of decimals.