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 octal digit represent?
Three. Each digit covers the values 0 to 7, which is exactly what three bits hold. Grouping bits in threes from the right and mapping each group is all the conversion is, which is why octal was popular on machines with 12, 24 and 36-bit words.
Why are file permissions written in octal?
Because permissions come in triads. Read, write and execute are three bits, so one octal digit describes one triad exactly. 111 is 7 (rwx), 101 is 5 (r-x), and 100 is 4 (r--). That is how 755 and 644 get their meaning.
What is 111111111 in octal?
777. Nine bits split into three groups of three, each group being 111, which is 7. That is the chmod value granting read, write and execute to owner, group and everyone else.
Why does one byte need three octal digits?
Because 8 is not divisible by 3. Eight bits split into 2 + 3 + 3, so the leading octal digit can only reach 3, and the largest byte, 11111111, comes out as 377. Hex avoids this problem entirely, since 8 divides cleanly by 4.
Can I convert several binary values at once?
Yes. Separate them with spaces, commas or new lines and each is converted independently in the same order, so a column of binary permission masks becomes a column of octal ones.