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Everything you send to an AI tool gets chopped into tokens, small chunks of text. A token is roughly three to four letters of English, so this sentence is about twenty of them. Pictures become tokens too, counted by their size rather than by what they show.

Tokens are how these tools charge you. If you pay per use, they are literally your invoice. If you pay a monthly fee, tokens come out of an allowance instead, and none of the vendors publish how much of that allowance one token uses. So I can tell you what something counts. I cannot tell you what it does to your limit, and I will not pretend otherwise.

That is the whole vocabulary you need. Everything on this site is a count of tokens, measured with the vendor's own free tools, on a named version, on a stated date.

Where to begin

A PDF page now costs less than a screenshot of it is the most useful habit to change today, and a fair look at what one of these tests actually is. Three files, one free counter, and the arithmetic printed out where you can check it.