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 many bits does one hex digit represent?
Exactly four. That is the whole reason hex exists: 4 bits map to a single digit 0 to F, so a byte is two digits, a 16-bit word is four, and a 32-bit value is eight. Grouping bits in fours from the right is all you need to do the conversion by hand.
Why does 00001111 give F rather than 0F?
Because leading zeros carry no value and the converter prints the number, not a fixed-width field. If you are writing a byte, pad the output to two hex digits, so F becomes 0F.
Can I convert several binary bytes at once?
Yes. Separate them with spaces, commas, or new lines and each is converted as its own number. Note that each token is treated independently, so 11110000 00001111 gives F0 F, not F00F.
Is hex only a different notation for the same bits?
Yes, and that is the useful mental model. Nothing is lost in either direction, only the notation changes. A hex dump is a binary dump with every four bits collapsed into a single character, which is why memory addresses, colours, and hashes are all written in hex.
How do I group the bits by hand?
Start from the right and split into groups of four, padding the leftmost group with zeros if needed. Then map each group: 1111 is F, 1110 is E, 1010 is A, 1001 is 9, and so on down to 0000 which is 0.