Diffhall Hall Pass $1.95/moFree during preview
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01Ask for work you can check 02Read the whole diff 03Keep secrets out of the code 04Treat every input as hostile 05Check who is asking 06Check that it exists 07Make tests able to fail 08Plan for when it breaks

Hall Pass $1.95/month or $19.50/year · one room $1.00 · Free during preview

Terms

Plain terms

October 2026.

  1. What this is. Diffhall is a self-study website with practice exercises. It is not a school, college or training provider and gives no degree, credit, grade, certificate or qualification.
  2. Practice, not advice. The benches use short, made-up examples. They teach you to spot kinds of problems; they are not a review or audit of your own software, and passing a bench does not make any code safe.
  3. Prices. Hall Pass $1.95 a month or $19.50 a year; one room $1.00, paid once. During the preview checkout is off and everything is free; nothing is charged. Subscriptions renew until cancelled; cancelling stops the next payment and keeps access to the end of the paid period.
  4. Your notebook. Keep its private link to yourself. You can delete it at any time.
  5. Fair use. Do not try to break, overload or scrape the site. Hand-ins are rate-limited.
  6. Content. The rooms, benches and notes are Diffhall's. Code on the benches is written for practice; secrets in it are placeholders and invented package names were invented on purpose. Do not install them.
  7. No warranty. The site is provided as it is. We check the facts and date them, but libraries and standards change.
  8. Who. Diffhall is run by WeldonPC (weldonpc.com), Ohio, USA.
  9. Questions. About these terms, a room or your notebook: Contact WeldonPC. Never send your notebook's private link; we do not need it.