I pasted a whole book into the counter and the page froze for a few seconds; is that normal?

What exactly was tested

These are the Word and character counter's own measurements, as its page states them, in Chrome on a desktop computer:

• Mixed Arabic and English text of about 1.5 MB, 100,000 short lines: counts appeared after 5 to 7 seconds.
• Of that, the text box froze for about 3 to 4 seconds just drawing the paste, before counting began.
• Counting runs in slices of roughly half a second or less, so the page stays responsive between them.
• A text of 15,000 lines, about 0.6 MB, is counted in about a second and a half.

Your device may be faster or slower, and another browser may behave differently, but the overall picture holds: the longest wait comes from displaying the text, not counting it.

What the tool does with long text

• Above about 120,000 units, the tool splits the text into pieces that end at line breaks, counts each piece and pauses briefly, showing 'Counting the long text…'.
• If you type or edit during counting, the old count is dropped and a fresh one starts on the newer text, so you never see a stale result.
• With large text the tool waits a little longer after your last keystroke before recounting, so it does not restart on every character.
• Above about 4,000 lines or 150,000 characters, the box shows every line in one direction, taken from the first letter of the text, instead of a direction per line. That changes the display only; the counts stay complete.

Counting a book more smoothly

1. After pasting, wait for the counts to appear, and do not paste again thinking the first attempt failed; that doubles the wait.
2. If the book is very large, count each chapter on its own and add the figures. Words, lines and sentences add up exactly as long as each chapter starts on a new line, which is the same way the tool adds its pieces internally. Characters in the whole book differ only by the line breaks joining the chapters.
3. Close other heavy tabs while pasting if your device is short on memory.
4. Note that a single very long line with no line breaks is counted in one go, because splitting happens only at line breaks. An ordinary book has plenty of breaks, so it does not run into this.

Are the numbers accurate at this size?

Yes. Splitting into pieces does not change the result, because pieces always end after a line break, and character, word and sentence boundaries always exist there. So a book's word count counted in pieces is the same as counted in one go. The only possible difference is the usual one between any two tools in their word-boundary rules, not anything caused by length.