Pick the number format, then type in either box. Works for hex, decimal ASCII and octal.
Every character has a numeric code. T is 84, r is 114. That number can be written in any base, and puzzles use three of them:
T is 54. Often written with a 0x prefix.T is 84.T is 124.Switch the format above and the codes are rewritten in the new base. The text stays the same.
Pairs of digits mixed with the letters A–F and nothing beyond F. English text is easy to spot in hex because lowercase letters fall between 61 and 7A and a space is 20. A string full of 6s, 7s and 20s is almost certainly text.
If every number is between 1 and 26, it's probably not ASCII. It's the A1Z26 cipher. If the numbers are between 32 and 126, decimal ASCII is the better bet. Codes above 255 are read as Unicode code points, so 9731 comes out as ☃.
Every two hex digits are one byte. 48 is 72 in decimal, which is H in ASCII, so 48 69 reads “Hi”. Paste the hex here, with or without spaces or 0x, and it converts as you type.
They're the same values written in different number bases. H is 72 in decimal ASCII, 48 in hex and 110 in octal. Use the format switch to move between them.
Text is encoded as UTF-8. Basic English characters are one byte each; accented letters, symbols and emoji take two to four.