Termcapsule

A class time capsule, opened by the teacher

How it works

How a class capsule works

You make a class and print a slip for each seat. Pupils open one link, type the code from their slip, write to their future selves and seal. On release day every code opens its own letter, and you can read them all. These are the rules the server keeps, in the order you meet them.

Last updated 28 October 2026

The rules, in order

  1. Your account. You sign in with a passkey: your phone or computer keeps a private key behind your fingerprint, face or screen lock. There is no password and no username. You get a recovery code once, and you can add up to 10 passkeys.
  2. A class. It has a name such as "Room 12, 2026", a grade band, a time zone and 1 to 40 seats. The name refuses @, web addresses and phone numbers, because it is printed and shown to pupils.
  3. Seats and codes. Each seat gets a code of 8 letters and numbers, printed in two groups of 4, using no I, L, O or U (if a pupil types O it is read as 0, and I or L as 1). Codes are shown once, in your open tab, for printing; the server keeps only a scrambled copy it cannot turn back into a code. A code works only together with the class link. 10 wrong codes in an hour from one network stop that network trying for a while, and the page names the time it can try again; you see the wrong-code count and can clear the lock. 300 wrong codes in an hour from everywhere pause the code box for the class.
  4. Slips and your sheet. The slips print 8 to a page: seat number, code and a square to scan. There is no name line. The last page lists the seats with a blank column you fill in by hand, so the link between seat and child stays on your paper and never reaches Termcapsule.
  5. Opening and writing. When you open the class, pupils write. Each one answers your prompts one screen at a time (up to 6, each answer up to 600 characters), then writes a letter of up to 3000 characters, 4000 in all. On classes with drawing on, they can also make a drawing with 8 colours. Text with an email address, a web address or a phone number is refused, and the page asks pupils to leave out their surname, address and phone number.
  6. Sealing. A pupil seals their letter when they are done, and sealing is final: nobody can read or change it until release day, the pupil and you included. The class seals when you press Seal now, or by itself at 23:59 on the close date. From then on nobody can change a letter, even if the server's scheduler has not run yet.
  7. Before release. Sealed letters are private until release. After release you, the teacher, can read every letter. You see only how many have sealed and which seat numbers, and the download of your data holds counts only. A pupil sees their own draft until they seal. If you give a seat a new code before the pupil seals, that code can open the draft, so the pupil's page says when the code was reissued. You can unseal the class before its close date (never after); every pupil's page and the release page then say so.
  8. Release. You release with your button, typing the class name to confirm, or on a date at 07:00 in the class time zone. A release date is 1 to 548 days ahead, after the close date. Pressing release twice releases once.
  9. After release. Each pupil's code opens their own letter and nobody else's, with a print button. You can read every letter on screen, download them, and print the sealed pack: one page for each seat that folds into an envelope marked with the seat and the date.
  10. Keeping and clearing. Letters are kept 180 days after release. The class then moves to your deleted classes with a notice, can be restored for 7 days, and is then deleted for good with its seats and letters. A class never released is cleared 548 days after it was made, and never before 180 days after its release date. A class you delete can be restored for 7 days.
  11. Shared tablets. Every time the pupil page opens it asks for a code. "Finished? Hand the device on" and sealing end a pupil's turn on the server, and a turn also ends after 5 minutes without typing, so the next pupil sees only the code box.
  12. When the server is busy or offline. The site runs within a free hosting allowance with daily limits. When saving is not possible the pupil page says so, keeps the words on screen with a Copy button, and keeps a copy on the device where the browser allows it, saying which.

Worked example

A grade 4 teacher makes "Room 12, 2026" with 26 seats in June, prints the slips and writes each child's name beside their seat on the teacher sheet. Pupils write on class tablets over two lessons; the class page shows "18 of 26 sealed", then 26. Writing closes on 20 June at 23:59. On the first morning back, 6 September, the letters are released at 07:00 New York time, and each child scans the square on their slip, types their code and reads what they wrote last June.

What it is not