English | 简体中文

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
Copies that quietly fail half-way	Post-copy verification — a local copy re-reads every copied file and hashes its content against the source; remote and cloud destinations get existence, size and a hashed sample. Either way the run ends on an exit code a script can act on
Copying between two servers is painful	Remote-to-remote relay via SSH tar pipe streaming
SFTP is disabled, or the box has nothing installed on it	Raw SSH tar streaming using the remote's own tar — duplicates hard-linked on the far side rather than sent twice

Quickstart

pip install blitcp            # CLI — zero dependencies, Python 3.8+

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

Optional: pip install paramiko for SSH, blitcp[cloud] for S3/Azure/GCS/SMB, xxhash for ~10× faster hashing. Prebuilt CLI and GUI binaries for Linux, macOS and Windows are on the Releases page — no Python needed.

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 — tar batches over raw SSH channels, local↔remote and remote↔remote relay (streamed through your machine, never stored)
• 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 (2m28s vs 3m16s /MT:1, verification ON)
SSH, 1,098 files / 1.1 GB over LAN	Level with scp -r (1m50.4s vs 1m55.4s, verify+dedup ON) via tar streaming — single run

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

The SSH row is one run, not a median of three, and to a Windows drive through WSL scp was ahead. Over SSH blitcp is not sold on speed: what it adds is verification, dedup and a resumable second run. Both runs, with the caveats.

Desktop GUI

pip install "blitcp[gui]" && blitcp-gui

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
• 简体中文 — README.zh-CN.md · DOCUMENTATION.zh-CN.md · glossary.zh-CN.md

Support

blitcp is free and Apache-2.0 licensed, and stays that way. Donations via Ko-fi or Liberapay go towards the Windows code signing certificate, hosting for blitcp.dev, and the hardware the published benchmarks run on. Starring the repository or filing a good bug report helps just as much.

License

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