What this tool does
It is the inverse of looking up a character’s code: give it numbers and it returns the text those code points spell out.
How it works
The input is split on spaces, commas, and newlines into individual tokens. Each token is parsed as a number — in decimal by default, or in hexadecimal when you pick the hex base or prefix the token with 0x. The tool then validates that the value is a legal Unicode code point: it must lie between 0 and 0x10FFFF and must not fall in the surrogate range 0xD800–0xDFFF, which Unicode reserves and which cannot stand alone as a character.
Valid code points are converted with String.fromCodePoint, which correctly produces characters above U+FFFF (such as emoji) instead of mangling them into surrogate halves. The decoded characters are concatenated into the output string.
Example and notes
In decimal mode, 72 105 33 decodes to Hi!. In hex mode (or with 0x prefixes), 48 69 21 likewise gives Hi! because those are the hex codes for H, i, and !. A higher code point such as 0x1F600 decodes to the grinning-face emoji 😀.
For code points 0–127 the output matches plain ASCII exactly. Tokens outside the valid range, or in the surrogate band, are reported as errors so you can spot a bad value rather than getting silent garbage. This pairs directly with the character-to-code tool for round trips.