Alpha software, not for production data. Bugs can cause data loss, formats may change without migration, and the cryptography has not been independently audited. Keep your own backups and check that you can restore from them.
Varsto

Storage format versions

From docs/spec/format-versions.md in the repository, rendered 2026-10-12.

Purpose

During alpha development, storage formats may change without migration paths. Once a format version is released, that version stays readable. This table tracks which released versions of Varsto can read each storage format, and whether standalone reader tools are available for data recovery.

Format versions

Format version First release Releases that read it Standalone reader tool Archived tag
0 (alpha-0) 0.0.1-alpha.0 0.0.1-alpha.0 to 0.0.1-alpha.3 none (varsto pull and varsto fsck of those versions) see the format version 1 note below
1 (compression, alpha-0-format.md section 16) 0.0.1-alpha.4 0.0.1-alpha.4 and later, including 0.0.1-alpha.12 none yet (varsto pull and varsto fsck of the same version) every tag from v0.0.1-alpha.4 on

Release rules

  1. Tag every alpha release (for example alpha-2026-10-08) with the source commit and binaries.
  2. Archive binaries and source on each release.
  3. Before publishing a new storage format version, ensure the previous version has a reader tool (built-in or standalone).
  4. Update this table before publishing each storage format version, with the release number and reader status.
  5. Once the product launches (first public release), every subsequent format change requires forward compatibility for at least one previous version.

Packs in 0.0.1-alpha.12 (format version 1 unchanged)

Small block objects are stored in packs (packs/; alpha-0-format.md section 30). Earlier versions do not read packs: a device on 0.0.1-alpha.11 or earlier misses every block another device packed. Update every device.

Block sizes in 0.0.1-alpha.11 (format version 1 unchanged)

Blocks are cut by file size (up to 16 MiB; alpha-0-format.md section 29). Objects, records and batches are unchanged and older readers read them, but no compatibility with the single set of block sizes of earlier versions is kept: a device on an older version cuts large files differently and cannot re-upload their blocks from its own copy, so update every device.

Ledger events in 0.0.1-alpha.9 (format version 1 unchanged)

A new ledger event, chunk_dropped (alpha-0-format.md section 23), records that a block was removed from a storage on purpose. Versions 0.0.1-alpha.8 and earlier reject a batch that holds an event type they do not know, so once any device moves data their pull fails: update every device first. From 0.0.1-alpha.9 on, unknown event types are read and ignored, so later event types do not break older readers. Objects, records and batch envelopes are unchanged; the local cached view moves to format 3 and is rebuilt once.

Format version 1 (0.0.1-alpha.4)

Chunk payloads are packed before encryption: one method byte (0 raw, 1 zstd level 12) followed by the data; compression is used only when it saves at least 5 %. Objects written by format 0 have no method byte and are not readable by format 1 readers; vaults created with format 0 are refused with a clear error. Readers: 0.0.1-alpha.4 and later. Archived tag of the last format-0 reader: v0.0.1-alpha.3.