matrix-spec/content/rooms/fragments/v1-stringy-power-levels.md

Power levels accepted as strings

In order to maintain backwards compatibility with early implementations, power levels can optionally be represented in string format instead of integer format. A homeserver must be prepared to deal with this by parsing the power level from a string. In these cases, the following formatting of the power level string is allowed:

• a single Base10 integer, no float values or decimal points, optionally with any number of leading zeroes ("100", "000100");
• optionally with any number of leading or trailing whitespace characters (" 100 ", " 00100 ");
• optionally prefixed with a single - or + character before the integer but after leading whitespace padding (" +100 ", " -100 ", "+100", "-100").