What counts as a character
Every character you type counts, including spaces and punctuation, unless you look at the "without spaces" figure. Characters are counted as actual Unicode symbols rather than raw computer storage units, so an emoji or an accented letter counts as one character each, the way a person reading the text would count it, not as two.
Worked example
For the sample sentence "The quick brown fox jumps over the lazy dog. It ran fast!" the tool reports 57 characters with spaces, 46 without spaces, 12 words, and 2 sentences.
Sentence and paragraph counts
The sentence count is an estimate, not an exact measurement: it looks for periods, question marks and exclamation points followed by a space or the end of the text, and tries to avoid mistaking a decimal point for a sentence ending. Abbreviations can still confuse it occasionally, so treat this number as a useful approximation rather than an exact count. Paragraph counting is unambiguous by comparison: it simply counts blocks of text separated by a blank line.
Platform limits
Common length limits, such as a 280-character post or a 160-character text message, are shown alongside your live count so you can see at a glance how much room you have left, or by how much you have gone over.