Your text stays in your browser โ it is not sent, not stored and not added to the address bar.
X uses weighted counting (emojis and many non-Latin characters count double, links always 23). SMS: a single character outside the GSM alphabet (e.g. an emoji or curly quotes) switches the whole message to Unicode with only 70 characters per SMS. Meta descriptions have no fixed limit โ 160 is a guideline.
JavaScript is required for the calculation.