Scanner not detected” doesn’t usually mean the device is damaged. It simply means your computer can’t reach the scanner service at that moment. That connection might run through a USB cable or your Wi-Fi network. If the operating system can’t talk to the right port, if the device is sitting on a guest network, or if the driver is looking for a path that no longer exists, scanning fails.
The solution is practical and brand-neutral:
Check the physical path, use the simplest driver your OS already trusts, and—if you’re on Wi-Fi—connect directly to the device’s IP address and keep that address stable.
This guide walks you through a sequence that works reliably on Windows and macOS without remote access, logins, or risky software.
Scope: Educational guidance only. You’ll learn the logic behind USB vs Wi-Fi scanning, clicking paths in Windows/macOS, how to reserve a stable IP for network scanners, and safe habits for ADF/flatbed use. No repairs or warranty services.
How scanning actually works
A printer-scanner has two separate internal services: print and scan. Your computer discovers each one through a driver.
• Over USB, discovery is nearly automatic.
• Over Wi-Fi, discovery depends on local broadcasts and network rules. If those broadcasts don’t reach your computer, or the device’s IP changes, the scanner doesn’t appear.
The fix is to simplify the path. USB gives quick proof; direct IP makes Wi-Fi stable.
Quick checks (2 minutes)
• Wake the device so its screen or Wi-Fi icon is steady.
• If using USB, test with a direct cable to confirm the scanner itself is fine.
• If using Wi-Fi, make sure the device is connected to your main network—not the guest network.
• Prefer built-in OS drivers (WIA/TWAIN on Windows, AirPrint/ICA on macOS).
• If using Wi-Fi, find the device’s IP and add the scanner by IP; then reserve that address in your router.
What common symptoms usually mean
| What you see | Likely cause | What to try first |
|---|---|---|
| USB works but Wi-Fi list is empty | Network discovery blocked or IP changed | Add by IP, reserve IP |
| Mac prints but won’t scan | Wrong protocol/driver | Re-add using AirPrint/ICA |
| Windows hangs on “searching” | Old WIA/TWAIN entry | Remove device, re-add clean |
| ADF scans are skewed | Roller/guide alignment | Clean ADF; use flatbed for important pages |
| PDF size is huge | High DPI or colour on text | Use 200–300 dpi greyscale |
Windows: from “not detected” to stable scanning
Windows talks to scanners through WIA or TWAIN. Heavy vendor suites often break when your network changes. A clean Windows entry with a current port is usually the most stable setup.
USB path (quick hardware proof)
- Disconnect Wi-Fi on the device temporarily and plug in a USB cable.
- Go to Settings → Bluetooth & devices → Printers & scanners.
- Open Windows Fax and Scan or the Scan app.
- Try a 200–300 dpi greyscale test.
If this works, the scanner hardware is fine—your network path needs fixing.
Wi-Fi path (clean re-add)
- On the device, find the current IP address.
- In Windows, remove old entries: Printers & scanners → Remove device.
- Add it manually: Add → Add manually → TCP/IP → enter the IP.
- Open your scan app and test.
- Reserve this IP in your router so the address stays stable.
If Windows scan apps hang, restart the print spooler and re-add the device cleanly.
macOS: let the system handle the heavy lifting
macOS works best with AirPrint/ICA. These methods bring both printing and scanning in one clean protocol.
Preferred method
- Go to System Settings → Printers & Scanners.
- Remove old entries.
- Add the device again using the entry that shows AirPrint or IPP.
- Test scanning in Preview or Image Capture.
If scan still doesn’t appear
- Confirm the device IP.
- Add it manually: Add → IP → enter IP → use AirPrint/IPP.
- Reserve the IP in your router.
USB vs Wi-Fi scanning: pick the right option
| Path | When to use | Advantages | Trade-offs |
|---|---|---|---|
| USB | First-time test or single-PC use | Quick, reliable | Cable required |
| Wi-Fi (auto discovery) | Simple home networks | No cables | Breaks on guest networks/mesh |
| Wi-Fi (add by IP) | Mesh/guest/VPN setups | Very stable | Needs IP reservation |
| Ethernet | If available | Most reliable | Needs cable nearby |
Permissions, VPNs & firewalls
VPNs can route your traffic away from your home network, making scanners invisible. Disconnect temporarily to scan. Firewalls can block discovery; adding by IP bypasses that. On macOS, private relay tools can also hide local devices—switching them off during setup helps.
ADF vs flatbed: what to use and when
Flatbed:Â best for important documents, photos, IDs, or anything fragile.
ADF:Â ideal for stacks of regular pages; keep sheets clean and squared.
Fixing skew or streaks
• Clean rollers with a dry microfiber cloth.
• Adjust paper guides properly.
• Remove staples or damaged edges.
• For wrinkled sheets, use the flatbed.
DPI, colour mode & file sizes
Documents look perfect at 200–300 dpi.
Use greyscale for most text documents—it keeps files light.
Use colour only when stamps or highlights matter.
Avoid scanning documents in photo-grade DPI unless needed.
Recommended workflows
| Goal | DPI | Mode | Notes |
|---|---|---|---|
| Email-ready document | 200–250 | Greyscale | Clear and small |
| Form with stamps | 300 | Colour | Keeps details visible |
| Photo on flatbed | 300–600 | Colour | Clean glass for best results |
| Archiving | 300 | Greyscale | Good long-term readability |
Troubleshooting at a glance
| Issue | What it means | What to do |
|---|---|---|
| Scanner never appears | Discovery or driver issue | USB test → Add by IP → Reserve IP |
| Appears then disappears | Address changes | Reserve IP |
| ADF skew | Guides/rollers | Clean and square |
| File too large | High DPI/colour on text | 200–300 dpi greyscale |
| Permission prompts | OS privacy rules | Allow scanner/camera access |
Make network scanning stable long-term
- Place the device near the router during setup.
- Find its IP address from its panel or router.
- Add it by IP in Windows/macOS.
- Reserve the IP in your router.
- Scan a test page at 200–300 dpi.
- Save a scan preset so future scans are quick.
Scan to searchable PDF (OCR)
OCR works best at 300 dpi greyscale with clean text.
Avoid strong shadows or tilted pages.
If OCR struggles, straighten or crop the scan first.
Monthly 60-second maintenance
• Wipe the flatbed glass.
• Clean ADF rollers gently.
• Replace the paper stack with fresh sheets.
• Confirm the reserved IP hasn’t changed.
• Do a one-page test scan.
Why does my computer print fine but cannot detect the scanner?
Printing and scanning run as two separate services. It’s very common for printing to work while scanning fails, especially over Wi-Fi. Your device might have picked up a new IP address, or your network may be blocking the discovery messages the scan app relies on.
The most reliable fix is simple: check the device’s current IP on its screen or in your router, remove the old entries on your computer, and add the device again using that IP. Use your operating system’s built-in driver (IPP/AirPrint on macOS or Standard TCP/IP/IPP on Windows). Once everything works, reserve that IP in the router so it stays consistent.
Is USB better than Wi-Fi for scanning?
USB is the fastest way to confirm the scanner hardware works because detection is automatic. If USB scanning succeeds, the device is healthy and the issue is the network path.
Wi-Fi is convenient, but it depends on stable discovery or a stable IP address. Adding the device by IP and reserving that IP gives you the convenience of wireless scanning without the usual connection drop-offs. If you have thick walls or tricky mesh setups, Ethernet is even more stable than Wi-Fi and behaves almost as dependably as USB.
What DPI should I use for documents, and why are my files huge?
For everyday documents, 200–300 dpi is all you need. Greyscale keeps the file size low while staying sharp.
Files get huge when documents are scanned in colour at very high DPI (photo mode). Save 300 dpi colour for forms that include stamps, signatures or detailed graphics. For long files, scan in smaller batches and combine them later so each part stays manageable. If you want a searchable PDF, run OCR afterwards—300 dpi greyscale usually gives the best results.
My ADF scans are skewed or streaky — how do I fix that?
Skew usually means the paper isn’t feeding straight or the rollers need cleaning. Open the ADF, clean the rollers with a dry, lint-free cloth and align the paper guides so they lightly touch the edges. Remove staples or curled edges that might catch.
If pages are fragile, bent or thick, switch to the flatbed for perfect alignment. A single streak across every scan often means there’s a tiny speck on the thin ADF glass strip—cleaning that area usually clears the line instantly.
Do I need vendor software, or are the built-in drivers enough?
In most cases, the built-in drivers from Windows and macOS are more stable and easier to maintain. They handle the essentials—DPI, colour modes, duplex scanning—without relying on heavy vendor apps that often break when the network changes.
Vendor software can help with specialised photo features, but you should first set up the device using the OS drivers. Only add extra tools if you need something specific that the built-in path doesn’t provide.
How do I keep scanning reliable month after month?
Long-term stability comes from a simple routine. Reserve the scanner’s IP so it stays the same. Add the device by IP so your computer doesn’t have to “discover” it each time. Keep the device on your main Wi-Fi network, wake it before scanning, and avoid extremely short sleep timers.
Once a month, clean the flatbed glass and ADF rollers, refresh your paper stack, and test a quick 200–300 dpi greyscale scan. A few minutes of basic care prevents most scanning issues before they start.