Word counts and keyword density for content.
With Paste your content = The quick brown fox jumps over the lazy dog.:
How often a word or phrase appears relative to the total word count: (occurrences / total words) x 100, shown as a percentage.
There is no official ideal number. Google does not rank pages by a density target - write naturally, since forced repetition can count as keyword stuffing under Google spam policies.
No - counting runs in your browser.