At 238 words per minute for silent reading and 130 for reading aloud. Those figures come from Brysbaert's 2019 meta-analysis of 190 studies, which is a more defensible basis than the "200 wpm" round number most tools use. Real speed varies a lot with text difficulty, so treat it as an estimate.
How are sentences counted?
By splitting on . ! and ? when followed by whitespace or the end of the text. Requiring the trailing space avoids the obvious false positives — "3.14" and "e.g." are not counted as sentence ends — but abbreviations followed by a space ("Dr. Smith") will still be over-counted. No purely mechanical approach avoids that entirely.
Is my text private?
Yes. Counting happens in your browser as you type; nothing is transmitted or stored. That matters more than it sounds for this particular tool, since word counters are often used on unpublished drafts and confidential documents.