Keeping a Photo Archive Unchanged: A Dated Receipt

November 4, 2026

London · November 2026

Tomorrow, Thursday 5 November, is World Digital Preservation Day. It is run by the Digital Preservation Coalition on the first Thursday of every November, and this year's theme is "Save our Stories (SOS): Our digital heritage in danger". The idea is simple: the records, pictures and memories we keep on hard drives are more fragile than they look, and somebody has to look after them.

I have a personal interest. Between 1999 and 2014 I photographed London's nightlife, film premieres and pavements, and this autumn I finished putting that archive in order: about 2,000 pictures across 575 sets, now licensed through Backgrid UK. Doing it properly meant opening thousands of files, checking captions against the camera clock, and rewriting the copyright and credit fields on the copies so they carry the right name. The originals stay untouched.

What can go wrong with an old file

Not much of it is dramatic. A drive fails. A file is opened and saved again by a program that quietly recompresses it. A caption is edited and the edit is forgotten. Two copies of the same picture drift apart over the years, and nobody can say which one is the original. None of that is anybody's fault, but when a picture is licensed, published or relied on years later, the first question tends to be the same: is this the same file it was?

Checksums, the archivist's old friend

Archivists have long answered that with a checksum, a short string worked out from the file's contents. Change a single pixel and the checksum changes. It is one of the quiet tools behind a lot of serious digital preservation. The catch is that a checksum on its own is just a string in a spreadsheet. It does not say when it was recorded, or by whom.

Where Partisan fits

That is the gap I now work on. I look after business development and communications for Partisan. Partisan records a file's fingerprint without seeing or keeping the document, gives a dated receipt, and shows a file is unchanged since it was recorded.

It is worth being clear about what that does not do. A receipt does not show that a picture is true, who took it, or when it was taken. It shows one thing well: that the file in front of you is the same file that was recorded on the date on the receipt. For an archive, a legal bundle or a set of business records, that is often exactly the question.

Save our stories

If you have an archive of your own, World Digital Preservation Day is a good excuse to look at it: where the files live, how many copies there are, and whether you could show next year that they have not changed. The Digital Preservation Coalition has plenty of free material for the day, and the hashtag is #WDPD2026.

If you would like to check whether your own files can be recorded this way, Partisan is at partisangateway.com.