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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?

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

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).