A digital time capsule that opens on the day you choose.

An Ancestorii capsule has a front and an inside. The front is what your family sees while they wait: a title, a short message and, if you like, a cover photo. The inside is what stays sealed:

• Photos and videos. Upload them, or pick them from your family Library.
• A letter. Each capsule has room for one letter, which starts from the prompt “Dear future me…” and shows who wrote it and when.
• Voice notes. Record them in your browser or upload an audio file. Each one shows who left it and when, and recordings are converted to M4A where needed so they play on any phone. More on voice notes.
• The people it is about. Tag a loved one and the capsule also appears on their Loved Ones page.

The things that make a capsule worth opening are usually the ordinary details that feel too obvious to record: what a normal Tuesday looks like, who sits where at Sunday lunch, what a loaf of bread costs, the song nobody can escape this year. Photos of the house, the street and the people as they are today will mean more in 18 years than one perfect portrait. Our guide to what to put in a time capsule has a longer list.

The Crypt of Civilization at Oglethorpe University is a time capsule the size of a room: 20 feet long, 10 feet high and 10 feet wide. It was sealed on 28 May 1940 and is not to be opened until 28 May 8113. Thornwell Jacobs, the university's president at the time, reasoned that the first known date in recorded history, 4241 BC, lay 6,177 years in the past, so the crypt should wait 6,177 years too. The 1990 Guinness Book of World Records called it “the first successful attempt to bury a record for any future inhabitants”.

Most capsules fare worse. The International Time Capsule Society, set up at Oglethorpe in 1990, estimates that 80 percent of time capsules will be lost “due to thievery, secrecy or just poor planning”. In practice that means a box whose location nobody wrote down, or an opening date that passes without anyone remembering.

A digital capsule takes care of the “where is it?” problem, because it sits in your family's account with its date on the front. It has weak points of its own: accounts get closed, services change and file formats age. So treat a capsule as the way something gets delivered on a date, not the only place it is kept. The Library of Congress advises keeping at least two copies of the photos you care about, stored “in different locations that are as physically far apart as practical”, and checking them at least once a year.

Choose a date that already means something to the people who will open it. Ancestorii does not send a reminder when a capsule opens, so a birthday or an anniversary is far easier to remember than a date picked at random. Dates that work well:

• An 18th birthday. A capsule made in a child's first years and opened at 18 is the classic. Ancestorii accounts are for people aged 16 and over (under-18s need a parent's consent), so they can have their own account in time to open it.
• A wedding anniversary. Seal the photos, the speeches and a letter to each other, then open them on your 10th or 25th.
• A new chapter. A first day at school, leaving home or moving house: seal what life looks like now and open it five or ten years on.
• A round number. Ten or twenty years from today. A short gap means the people who sealed it will probably open it; a long one makes it a gift to the next generation.

You can change the date as often as you like until you seal the capsule. After that, it is fixed.

A capsule belongs to My Family, your family's private space on Ancestorii. Only members of your family space can see it. It never appears on Our Stories, Ancestorii's public story feed, or in search results.

Inside the family, everyone can see that a capsule exists. Its card shows the cover photo, title, short message, opening date and a countdown such as “2 years 3 months remaining”. The photos, videos, letter and voice notes inside stay locked in Ancestorii until the date, then open for everyone in the family space.

The seal is there to keep a surprise, not to guard a secret. Do not use a capsule for passwords, legal papers or anything that must stay hidden from your family.

Ancestorii is a private library for a family's photos, voices and stories, and capsules are one part of it. A capsule can draw on photos already in your family Library and be tagged to the people it is about, so it sits alongside their albums and timelines rather than in a folder of its own.

Capsules are unlimited on both plans. The Free plan costs nothing and includes 1 GB of storage for the whole family, with files up to 20 MB each. Premium is £3.99 a month for the whole family, with 100 GB and files up to 10 GB (see pricing). If the words will not come, Story Assistance, Ancestorii's optional AI writing help, can suggest a two-paragraph letter, a description and ideas for what to say in a voice note. You choose what to keep.

What it does not do: send an alert on the day, or make capsules in the phone app.