BLIT
Big files, moved fast, proven intact.
A native Mac app for moving large files between SFTP servers, external drives and NAS shares. Every file is checked by SHA-256 where it lands, before it gets its real name.
Item
Throughput · 60 s
Link data
Log
Warning
Verified, not assumed
Hashed on the server
Blit asks the server for each file's SHA-256 while the file is still in its cache, and hashes its own copy as the bytes arrive. The two have to match before the file gets its real name.
Until then it's a .blitpart. A half-written file never sits under a real name.
The check runs alongside the download and shows its own progress and time left, on the server, the NAS or a read-back, so a 70 GB file never just sits at "verifying". Want raw speed instead? Switch to size checks in Settings; moves still verify.
Hashed on the NAS
Copies to a Synology share are checked by sha256sum on the NAS itself, over SSH, so a copy can't pass by coming back from the Mac's own cache.
94% of a 1 GbE link's line rate, every file verified on the NAS.
Never quietly downgraded
An interrupted hash is never accepted as "size looks right". Size-only checks are labelled everywhere they appear, and a move deletes a source only after its copy's hash has matched.
Proof you can look up
Every file lands in the Transfer Log: size, hash, how it was verified, and when. Search it by name or SHA-256, and export it as CSV.
Fast across an ocean
Tuned for a server 148 ms away, where one stock SFTP connection crawls. Parallel connections, pipelined reads, and a receive buffer bigger than macOS allows by default: 22.5 TB a month in about 4.7 days instead of 24.5.
Measured from the Mac to a server 148 ms away, same server and network for every method. Verification runs alongside the transfer, or can be switched to size checks for raw speed.
Resumes anything
Each part file records which byte ranges are on disk. Quit, sleep, lose Wi-Fi, unplug the drive: the queue survives and picks up mid-file.
A queue you steer
Pause, resume, reorder, cancel, Retry Now. Downloads and drive-to-NAS copies run side by side in separate lanes. A full disk waits for space instead of failing, and Blit offers to empty that drive's Trash to make room.
Shares come back
When the NAS sleeps or the network drops, queued copies wait for the share, then Blit remounts it with the password macOS already saved. No dialog, no trip to Finder.
Says why it's slow
The HUD shows the round trip, the route (and warns when Wi-Fi carries it while a cable is plugged in), and says when the server's disk, not the network, is the limit.
The HUD
Everything else in Blit is a plain Mac app. Status and motion get a 1-bit, pixel-terminal instrument, inspired by 1-bit pixel art and the Nostromo's screens: black and grey, with muted red reserved for failures. Every state has a glyph or a word, never color alone.
A real Mac app
Finder-style browser
Servers, drives and NAS shares in one sidebar. Newest first, search (⌘F), Get Info, Open With, undo, favorites, and two panes to drag between.
Quick Look plays what Finder's does, MKV included once QuickLook Video is installed.
Rename N items
Replace, add or format names in bulk, with a live preview, multi-step rules and presets for your naming conventions.
Copy to / Move to
Send reviewed files to a NAS folder without dragging. A move removes each file only once its copy is verified.
Already there? Blit asks: Replace, Keep Both, Skip or Stop.
Menu bar at a glance
Time left, at a width that never nudges its neighbours, while the arrow's tray fills. A download and a NAS copy at once show as two lines, one per lane.
A failure leaves a red until you've seen it. The Mac stays awake while Blit works.
Notifications that report
Copied to Movies · 71.6 GB · verified on the NAS · 11 min at 108 MB/s.
Show in Finder when it's done, Show Details when something needs you.
Room when you need it
Deleted files keep their space until the Trash is emptied. Empty one drive's Trash from the sidebar, or straight from a transfer waiting for room.
Out of the way
The full HUD opens when a transfer starts and steps back to the strip once everything has verified. Anything that needs you keeps it open.
Keeps itself current
Signed updates, checked once a day and installed in a click from Blit › Check for Updates.
Spec sheet
| Platform | macOS 27, Apple silicon. SwiftUI and AppKit, following the Human Interface Guidelines. |
| Transport | SwiftNIO SSH with Blit's own pipelined SFTP v3 client. Password or ed25519 / ECDSA keys, stored in the Keychain. |
| Verification | SHA-256 on the server (with a hash cache), on the NAS, or by read-back, labelled by strength. |
| Resume | Byte-range state beside each part file, a durable queue, and retries with backoff. |
| Preview | The system's Quick Look, including formats that Media Extensions add (QuickLook Video: MKV, WebM, AVI). |
| Updates | Sparkle, with EdDSA-signed releases, checked daily (or off in Settings). |
| Trust | Host keys pinned, known_hosts honoured (hashed entries too), and a changed key refused. |
| Distribution | Sold directly, one-time, through Lemon Squeezy. Builds are signed with Developer ID and notarized by Apple. |
Price
- 7-day free trial, everything included
- 30-day refunds, no questions asked
- Updates to Blit 1.x included
- After the trial, transfers already queued still finish