What's new

Recent changes to the SQZ engine, newest first, in plain words. Everything under "In development" is in the current development build and not yet in a numbered release.

In development (September 2026)#

Desktop app#

• SQZ Backup for Windows and macOS Early preview: backup plans with schedules through Task Scheduler or launchd, keep rules applied after each run, a snapshot list, restore into a new folder, and the password in Credential Manager or the Keychain. More

Backups#

• For programs that run sqz: --json on backup init, run and list, and --password-stdin to pass secrets on standard input instead of environment variables. More
• Faster S3 uploads: packs are uploaded four at a time, and copy moves four objects at a time. Still tested against a simulated server only. More
• Hard links and --usn: a full scan counts files with several names, and while any exist --usn scans everything and says why. More
• Windows metadata in backups Testing on Windows: file attributes and alternate data streams are stored and restored, and restore --acls restores permissions. More
• NTFS change journal Testing on Windows: --usn-check compares the journal with a full scan; --usn reads only the folders the journal names, with guards. More
• Shadow copies Testing on Windows: run --vss backs up a frozen copy of the drive so open files are consistent. More
• S3-compatible buckets for repositories and replicas, with request and byte counts after each command. Tested against a simulated server only. More
• copy and drill: keep a replica without the password; rehearse a restore without writing. More
• Retention: forget, prune, protect and unprotect. More
• sqz backup (preview): encrypted, deduplicated backup repositories. More

Archives#

• Safer restores of damaged entries: a damaged or crafted JPEG, PNG, ZIP, gzip or PDF entry is refused cleanly instead of reserving gigabytes of memory or looping. Found by fuzzing. More
• Faster appends to archives with many small files: 2.4 to 2.7 times faster; a 1%-changed append of 1,000,000 files went from 36.6 s to 14.9 s.
• sqz estimate: time, size and memory before a big job, shown automatically for 1 GiB or more. More
• sqz-extract, a standalone extract-only program for Windows, Linux and macOS. More
• Destination checks before writing: existing files, case clashes, names Windows cannot create, and free space are caught before any file is written. More
• Faster extraction when files share data: each block is decoded once, in parallel. A 162 MB app set went from 475 s to 144 s on 4 cores.
• sqz zip: export a snapshot as a verified standard ZIP. More
• Many-snapshot archives are up to 11.8 times smaller and append in 0.7 s instead of 13.4 s, thanks to snapshot edits and chained indexes. More
• Format v7: folders, symlinks, hard links, permissions and sub-second times are kept. More
• --smart: an opt-in per-block cost planner. More
• x86 branch filter for programs (format v6): a 27.4 MB set of Linux tools went from 8.2 MB to 7.4 MB with Balanced.
• sqz probe: measure each transform's gain and cost on your files.

Windows#

• Right-click menu in Explorer: compress with four modes or with options; extract, export to ZIP and test .sqz files. More
• Sharp progress windows at 125% and 150% scaling, labelled modes, and the SQZ icon.
• SQZ is no longer confined to the efficiency cores of hybrid CPUs on Windows 11.

Safety#

• Fuzzing of archives, the index, codecs, the SQCM decoder, transforms and chunk layouts, with AddressSanitizer on Rust and C++.
• An independent Python reader written from the format specification, checked against every test archive and every single-byte corruption.
• Crash-injection tests that tear an append at every byte.
• A crafted archive can no longer force large memory reservations.

0.9.1: Atlas foundation#

• Full 256-bit BLAKE3 identities for every piece (format v5), verified on every read.
• Extraction and new archives are staged and published only after they are complete and verified; nothing is overwritten.
• --file to extract or test chosen files, decoding only the blocks they need.
• Balanced and Max compare their result with zstd and keep the smaller.

0.9.0#

• --model-family for related safetensors checkpoints, with exact XOR deltas and float layouts.
• Verified JPEG recompression in Balanced and Max.
• --no-transforms for comparisons, and a much richer benchmark tool.
• Format v4.