Fair questions.
Honest answers.

Yes. To Chris, the person behind this experiment. This is a voluntary personal contribution, not a charitable fundraiser or an investment. You receive no financial return.

Yes, by PayPal: send $0.01 to a friend from your PayPal balance or bank and the whole cent arrives with no fee (the first PayPal penny did exactly that). That is the US rate. Sending from outside the US, PayPal bills the sender 5 percent with a 99 cent minimum on friend payments, so a penny costs about a dollar at your end and the jar still receives exactly one cent. From abroad, the 50 cent card option is the cheaper way once it is open. If you pay by card inside PayPal, or mark it as goods and services, PayPal charges a fee; the allowance box covers it if you want. Card networks on this site will not move less than 50 cents, so the card option is 50 cents: one penny counts toward the goal, the card company keeps about 31 cents, and what is left is listed separately as a fee allowance, never toward the goal. Venmo is coming.

The card processor takes 2.9 percent plus 30 cents out of a card gift, and PayPal takes up to 3.49 percent plus 49 cents when a gift is paid by card or marked goods and services. Tick the box and that amount is added on top, so the full amount you chose arrives as pennies. It is off by default. The allowance is always listed separately and never counted toward the goal. On PayPal, paying a friend from your balance or bank costs nothing, so leave the box off there.

For overachievers. A dollar is 100 pennies and the fee is small by comparison. Your amount is always shown before you pay, and the counter counts it as that many pennies, not that many people.

Yes. Pick Crypto in the chooser for Bitcoin, Ethereum and Solana addresses (USDC too). Crypto gifts are checked and logged by hand within a day at the dollar value when they arrive.

A link that is yours, like sendonepennyto.me/r/ABC123. Sign up with an email and first name to get one. Anyone who arrives through it is counted as yours: visits, signups and pennies, including the people they bring. The Spreaders page shows the biggest networks by first name, only for people who ticked the box. No password, no account, and the email only gets a few updates a year with a one-click leave link.

No recurring contributions are planned. One time means one time.

Then don’t. Enjoy the joke, share the link if you like, and keep your penny. Participation is optional.

Yes. It only moves when a payment is confirmed by the processor, and every entry is listed on the ledger with its time, method and amount, and nothing about who sent it. Payment count is not a count of unique humans.