Prefix every line with a number. Pick the start, separator and zero-padding.
Paste your lines, set the starting number and choose a separator (period, parenthesis, colon, dash or tab). Each line gets its number prefixed instantly.
Yes. Tick zero-pad and numbers align to equal width (01, 02, ... 10), which keeps lists tidy when there are 10+ lines.
Completely free, no sign-up, runs in your browser.