A little Mac utility for a very specific problem
A small fix for
printer gibberish.
My HP Color Laser MFP 178nw sometimes printed symbols instead of my documents. I built this app around the header-buffering workaround I tested, with a simple switch in your Mac’s menu bar.
Developer ID signed & Apple notarized
Use at your own risk. No warranty or liability to the maximum extent permitted by law. Read the notice ↘
44 bytescollected at the start of each job
Same document dataforwarded byte for byte
Entirely localno accounts or document uploads
The fix
Give the printer
the whole beginning.
During my investigation, a failed job started with just UNIR in its first piece of image data. The rest of the format identifier and header arrived later.
I replayed the same captured two-page data with different framing. The split-header variants printed gibberish; the complete-header variants printed both numbered pages correctly.
The app collects the complete opening header before writing it to the print backend. It then streams the rest of the job unchanged.
- 8 bytes
UNIRASTplus its terminating zero- 4 bytes
- The page-count field
- 32 bytes
- Dimensions, resolution, colour and page settings
Then the document keeps flowing. A large job uses the same opening header size as a small one.
Before you install
Use at your own risk.
The app requires you to read this notice and choose Agree & Continue before it runs a printer helper. Decline & Quit closes the app.
HP178nw Header Buffer is an independent, experimental printer workaround. Use it entirely at your own risk.
The software is provided as is and as available, with no warranties, promises of reliability, or guarantees of fitness for your printer or Mac.
To the maximum extent permitted by applicable law, the developer accepts no responsibility or liability for any claim, damage, cost or loss arising from installing, using, or being unable to use this software. This includes printer problems, failed printing, wasted paper or toner, data loss, and interruption of work.
You accept responsibility for your use and its consequences. Nothing in this notice excludes liability or rights that applicable law does not allow to be excluded.
Choose Agree & Continue only if you accept this notice. Decline & Quit closes the app. If you already have a buffered printer installed, declining does not remove that existing queue or filter; use the removal app to uninstall them.
Get set up
A separate printer.
A familiar way to print.
Your original printer and scanner stay available. Setup creates a separate AirPrint queue that applies the workaround.
- 01
Copy & read the notice
Open the downloaded DMG and drag HP178nw Header Buffer to Applications. Open it, read the responsibility notice, and continue only if you accept it.
- 02
Choose your HP printer
First add your HP 178nw using AirPrint in System Settings if needed. In the app, select that original queue and approve the one-time administrator prompt.
- 03
Try the sparse test
Print the included two-page low-toner PDF from Preview, choosing the buffered printer. Check both numbered pages. Cancel at the printer if gibberish starts.
On selects the buffered printer for new jobs.
Off returns to your original printer when the buffered one is selected.
Your choice is remembered. Jobs already queued keep their existing queue.
To restore your saved On/Off choice after a restart, add the app in System Settings → General → Login Items & Extensions → Open at Login. The installed queue and filter stay in place even when the menu app is closed. Print dialogs can override your default printer, so check the selected queue.
Good to know
A few sensible
questions.
I built this independent utility after investigating my own printer. Here is what it does and what I have tested.
Will it work with large documents?
The filter has no document-size or page-count limit of its own. It collects the first 44 bytes once per job, then passes the remaining data through in blocks of up to 64 KB. It does not hold the whole document in memory.
The design does not require a larger opening buffer for a larger document. The printer’s normal limits still apply, and I have not tested every document or measured long-term reliability.
Why exactly 44 bytes?
That is the complete opening structure of these Apple Raster jobs: an 8-byte format identifier, a 4-byte page-count field, and the first page’s 32-byte header. I chose a complete header because it worked in the controlled comparisons. I have not established the smallest working buffer size.
You can see the layout in the CUPS raster implementation. macOS still controls how the outgoing network traffic is packetized.
Which Macs and printers does it support?
The app includes Intel and Apple silicon executables, with a macOS 11 minimum for the launcher. It is scoped to the HP Color Laser MFP 178nw with a compatible existing AirPrint profile. Setup checks for the required system Perl and CUPS filter path before installing.
It is not a general fix for every HP model. CUPS has deprecated PPD-based drivers, so a future macOS release may remove a component the workaround needs.
Does it change or upload my document?
The filter forwards every byte of the raster data unchanged. It only collects the beginning before passing it on. Your Mac continues to print directly to your printer; the app adds no document uploads, accounts, traffic capture or telemetry.
This download page has no analytics scripts, forms or accounts. Cloudflare serves the page and download files.
Does the workaround survive a restart?
Yes. The installed printer queue and filter remain after a restart, and the filter applies to jobs sent to the buffered printer. To bring back the menu icon and restore your saved On/Off choice when you log in, add the app to Open at Login in System Settings → General → Login Items & Extensions.
For consistent selection, choose the buffered printer as your default in Printers & Scanners. An app can still print through a different queue if you choose it in the Print dialog.
What happens if I quit the app?
Quitting closes the menu-bar icon. The selected printer stays selected, and the filter continues to run for jobs sent to the buffered queue. Use Off before quitting if you want the original printer selected.
Can I remove it completely?
Yes. Quit the app, remove its Login Item if you added one, and finish or cancel jobs on the buffered queue. Open Remove HP178nw Header Buffer from the DMG’s Support folder and approve removal. Then delete the apps.
Deleting only the main app leaves its printer queue and filter installed. The removal app removes the separate buffered queue and its marked helper, keeping your original printer.
What is included in the download?
The main app, an Applications shortcut, and a Support folder with the removal app, instructions, disclaimer, readable app sources and the low-toner test PDF. The package contains no captured documents, traffic traces or printer logs.
Version 1.2.3 adds the required first-use responsibility notice. It retains the printer-chooser and setup-path fixes, with the same tested printing filter.
Open source · MIT license
Build it yourself.
I have published the complete app and helper sources under the MIT license. You can inspect the workaround, change it, or build both Mac apps yourself.
The package includes the menu app, installer, removal tool, filter, artwork and offline tests. No Apple Developer account or signing credentials are needed for a local build.
Source for version 1.2.3 · 1.6 MB
A standalone local build.
On a Mac with Python 3.9+ and Apple Command Line Tools, open Terminal in the extracted folder and run:
python3 tests/test_offline.py
python3 build.pyLocal builds use an ad-hoc signature. The prepared app download below is signed with Developer ID and notarized by Apple.
Download source ZIPHP178nw Header Buffer 1.2.3
Give it a try.
Free download. Signed with Developer ID,
notarized by Apple, and ready to copy to Applications.
Use at your own risk. Read the responsibility notice before installing.
Verify your download
SHA-256 · DMG · 3.2 MB
18fcf455b27845e67017efa7346cc7e3f8c5acca591bf742afd0a2828009c748Download checksum The disk image and both enclosed apps carry their Apple notarization tickets. No macOS security settings need to be disabled.