blitcp — High-Speed File Copier with Deduplication & SSH Streaming

blitcp is the new name of fast-copy (renamed in v4.0.0 — "blit" as in bit-block transfer, which is what the block-order engine does). Existing installs upgrade in place via --update; on-disk state and FAST_COPY_* environment variables keep working. See the CHANGELOG.

A fast, cross-platform tool for copying files and directories at maximum sequential disk speed — built for USB drives, external HDDs, NAS backups and large SSH transfers. CLI + desktop GUI, in 7 languages.

Why blitcp?

Problem	Solution
cp -r is slow on HDDs due to random seeks	Reads files in physical disk order for sequential throughput
Thousands of small files copy painfully slow	Bundles small files into tar stream batches
Duplicate files waste space and time	Content-aware dedup — copies once, hard-links or reflinks the rest
No space check until copy fails mid-way	Pre-flight space check before any data is written
Silent corruption on cheap USB drives	Post-copy verification confirms integrity
Copying between two servers is painful	Remote-to-remote relay via SSH tar pipe streaming
SFTP is slow	Raw SSH tar streaming bypasses SFTP overhead — 3–5× faster

Quickstart

Prebuilt CLI and GUI binaries for Linux, macOS and Windows are on the Releases page — no install needed. Or run from source:

pip install paramiko          # SSH support; xxhash optional (~10× faster hashing)

blitcp /data /media/usb/data                # local → local
blitcp /data user@host:/backup              # local → remote over SSH
blitcp user@host:/data s3://bucket/backup   # any combination of local/SSH/cloud
blitcp --help                               # everything else

Key features

• Block-order reads — files are read in physical disk order (FIEMAP/fcntl/FSCTL), eliminating random seeks on HDDs
• Reflink copies on btrfs / XFS / APFS / bcachefs — metadata-only CoW clones make a 10 GB same-volume copy complete in milliseconds
• Content-aware deduplication — xxHash-128/SHA-256; each unique file is copied once, duplicates become hard links or reflinks, with a cross-run SQLite cache
• SSH transfers without SFTP — chunked ~100 MB tar batches over raw SSH channels, local↔remote and remote↔remote relay
• Cloud object storage — s3://, az://, gs:// as source or destination, with encrypted saved connections and a built-in passphrase generator
• SMB / UNC shares — copy straight to \\server\share with saved credentials
• Sparse-file awareness — VM images copied via SEEK_DATA/SEEK_HOLE; holes never hit the wire
• Faithful metadata — permissions, timestamps, owner, xattrs and POSIX ACLs / NTFS DACLs+ADS, matching cp -a
• Safety rails — pre-flight space check, post-copy verification with proper exit codes, honest dedup accounting on FAT32/exFAT
• --use-sudo self-elevation with a tamper-resistant (chattr +i) JSONL audit log
• Interface in 7 languages — English, Ελληνικά, 中文, Deutsch, Italiano, Español, 日本語
• Multiple sources, globs, single-file renames — cp -r-style ergonomics across every mode
• Works on Linux, macOS, Windows (long paths included) · Synology/busybox-friendly · self-updating

Measured, not marketed

Scenario	Result
Linux, 12,347 small files, cold HDD → SSD	2.5× faster than cp -ar (5.9s vs 15.0s, dedup+verify ON)
Windows, 9,578 files off USB 2.0	1.3× faster than robocopy — with verification ON
SSH, many small files over LAN	3–5× faster than scp/SFTP via tar streaming

Full methodology and more scenarios: blitcp.dev/benchmarks · DOCUMENTATION.md

Desktop GUI

pip install PySide6 && python blitcp_gui.py

Transfers, saved connections, file browser, history and settings — same engine, point and click. More screenshots →

Documentation

• blitcp.dev/docs — guides: local copies, SSH transfers, cloud storage, sparse files, everyday options
• DOCUMENTATION.md — the full manual: every option, how it works internally, examples, benchmarks
• CHANGELOG.md — release history

License

Apache License 2.0 — see LICENSE. The --index-existing / --dedup-existing features were contributed by York-Simon Johannsen (#3).

Support

blitcp is free and open source — the best way to support it is to help it grow:

• ⭐ Star the repository and share it with anyone who moves a lot of data
• 🐛 Report bugs and ideas via issues or pull requests

If you'd like to make a donation, please get in touch.