A container file format that attaches metadata to a file.
A .slpc file is a ZIP archive holding a content file of any type together with a TOML document, the flyleaf, describing it. The two become one file, so copying, moving, or sending the content file carries its flyleaf along.
Most files have nowhere to put metadata. Some formats have an embedded slot, but writing to it means modifying the file itself, and a great many types have no slot at all. Filenames carry very little. Sidecar files sit beside the file until someone copies one and not the other. Databases hold metadata well until the file leaves the system, and then the two are separated with nothing to reconnect them.
A container needs no special tooling to make or to read:
cat > slipcase.flyleaf.toml <<'TOML'
slipcase_version = "1.1"
[content]
file = "report.pdf"
TOML
zip report.pdf.slpc slipcase.flyleaf.toml report.pdfThat is a conformant container. unzip gets it back.
SPEC.md is the specification. DESIGN.md records the design and the reasoning behind each rule.
https://slipcaseformat.org presents both as web pages, alongside the implementations that exist. The site is generated from this repository and this repository stays the authority: where the two differ, these files are right and the site is stale.
To the extent possible under law, Excelano LLC has waived all copyright and related or neighboring rights to Slipcase, dedicating it to the public domain under CC0 1.0. Anyone can implement it — or quote, fork, or embed the text — without obligation to this project.