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.
Do I need to separate the bytes with spaces?
No. All whitespace, commas and 0x prefixes are removed before decoding, so a continuous string works exactly like a spaced one. What matters is that the total number of hex digits is even.
Why does an odd number of digits give an error?
Because a byte is two hex digits, so an odd count means one digit has no partner. The tool refuses rather than guessing whether the missing digit belongs at the front or the back, since either assumption would silently corrupt the output.
Can I paste a hex dump straight from xxd?
Only the hex column. The offsets on the left and the ASCII preview on the right contain characters that are not valid hex, so they will be reported as invalid. Cut the middle column out first and the bytes decode cleanly.
Why do two hex bytes turn into one character?
Because the bytes are decoded as UTF-8, which is a variable-length encoding. c3 a9 is a valid two-byte sequence for an accented e, so it produces one character. Bytes below 80 are single-byte ASCII characters and decode one for one.
Does the case of the hex digits matter?
No. Upper and lower case are treated the same, so 48 65 4C and 48 65 4c decode to the same three characters. Only characters outside 0-9 and a-f are rejected.