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 turn RGB values into a hex colour?
Convert each channel on its own and pad each result to two digits. RGB(30, 144, 255) gives 1E, 90 and FF, which becomes #1E90FF. Do not paste the three numbers together, they are three separate bytes rather than one 24-bit value.
Why is 15 shown as F rather than 0F?
Because the converter prints the number without assuming a width. 0F only makes sense when you have decided the value lives in a byte. Pad the output to two characters yourself when you need byte alignment.
Why is the hex output uppercase?
It is the common convention for constants, colours and hashes, and hex is case-insensitive anyway, so FF and ff are the same value. Lowercase it after copying if your codebase prefers that.
Does the output include a 0x prefix?
No. The tool prints the digits only, so you can paste them into a colour, a config file, or a #define without stripping anything. Add 0x yourself if the target language needs it.
How large a number can I convert?
Effectively any size. Parsing uses arbitrary-precision integers, so a 20-digit decimal converts to exact hex, where a spreadsheet or a plain JavaScript number would start rounding above about 9 quadrillion.