Every AI answer on this site comes with a receipt.

Model races, a daily guessing game, and a tokenizer you can poke — priced to six decimal places. Your visit costs $0.00: the defaults replay recordings, and live runs are opt-in and capped.

Model Arena — one prompt, three or four models, every answer priced to six decimals; the winner is arithmetic (correct → cheapest → fastest). No voting, no vibes: a deterministic, priced race over recorded challenges. Opens on letter-count, the race the priciest lane got right. Guess Which AI — one odd prompt, three anonymous answers, some days a fourth written by me. Name the model; the reveal prints each answer’s model, capture date, and exact price.

What does text cost?

TOKEN RECEIPT2026-07-28
GPT-4.1 nano
input — 0 tok × $0.10/MTok $0.000000
GPT-5.4 nano
input — 0 tok × $0.20/MTok $0.000000
Claude Haiku 4.5
input ~ 0 tok (est.) × $1.00/MTok $0.000000
Claude Sonnet 5
input ~ 0 tok (est.) × $2.00/MTok $0.000000
TOTAL if sent to all four$0.000000
OpenAI counts exact (o200k) · Claude counts est. ±20% · prices: provider list, verified 2026-07-09
How these numbers are made

Tokens are the chunks a model actually reads — about three-quarters of an English word each, so 100 words is roughly 130–140 tokens.

OpenAI rows are exact. Your text is encoded in your browser by the gpt-tokenizer library using o200k_base, the same encoding OpenAI’s models use. Same input, same count, every time.

Claude rows are estimates. Anthropic doesn’t publish its tokenizer, so there’s nothing exact to run. I multiply the o200k count by 1.15 and mark it “est.” — read ±20% into it. Where this site has real Claude numbers — Arena races and Guess reveals — they come from Anthropic’s own usage reports, and those are exact.

The math on every line: tokens × rate ÷ 1,000,000 = the line’s cost, rounded to six decimals at display — recompute any line by hand. Rates per million tokens (MTok), as listed by OpenAI and Anthropic, verified 2026-07-09: GPT-4.1 nano $0.10 in / $0.40 out · GPT-5.4 nano $0.20 in / $1.25 out · Claude Haiku 4.5 $1.00 in / $5.00 out · Claude Sonnet 5 $2.00 in / $10.00 out.

The receipt prices sending your text, so lines use the input rate; what a reply would cost depends on its length (output rates above).

Nothing you type leaves the page — the counting runs in your browser. The headline’s own token boundaries are computed once, when the site is built. Your text is tokenized live, on your device.

That tokenizer is the live demo — exact OpenAI counts in your browser, Claude counts labeled as estimates. All projects — seven builds, this tokenizer included; receipts where the facts have landed.