Windows 10 Mobile Offline Update Guide (Windows Phone 8.1 → Windows 10 Mobile 10586.107)

This guide compiles two sources — an English technical walkthrough and a Bengali community tutorial — into one consolidated reference for using the community “Offline Update Project” (iutool) to push Windows 10 Mobile onto Lumia and other Windows Phone 8.x devices that Microsoft’s official Upgrade Advisor no longer supports. Since Microsoft shut down WP8.1 update servers in mid-2017, this offline .cab deployment method (built around Microsoft’s own iutool.exe/getdulogs.exe binaries) is the only way to move these devices to Windows 10 Mobile.

⚠️ Before You Start

This is an unofficial, community-built process. It repurposes Microsoft’s own deployment tooling but is not supported by Microsoft. Proceed at your own risk — a failed flash can leave a device unusable.
Back up everything first: photos, videos, documents, and contacts, to your PC or a memory card. Perform a factory reset of the phone before starting is recommended by the Bengali guide, and removing your PIN/screen lock is strongly recommended by both sources to avoid the device becoming unresponsive mid-update.
Charge the battery to at least 80% (English source) — the Bengali guide and the original XDA thread simply say a full charge is recommended, and note the process can proceed even below 40% but isn’t advised.

Prerequisites

Requirement	Detail
Starting OS build	At least 8.10.14219.341. If your phone is older, update it through normal channels first.
Free storage	At least ~2.5 GB free internal space.
Unsupported hardware	Any 4 GB ROM device (e.g. Lumia 530, HTC 8S, Huawei Ascend W1) — the partition layout can’t fit the upgrade. HTC 8X/8XT are also unsupported (MainOS partition too small).
Host PC	Windows 7 SP1, 8, 8.1, or 10, with the Windows Phone USB drivers installed (via Windows Update or the Windows Device Recovery Tool) and all Visual C++ Redistributables installed.
Cable/port	A good-quality data cable in a USB 2.0 port — older USB 3.0/USB-C controllers can drop packets mid-transfer.
Developer Mode	Enable via Settings → Update & Security → For Developers on the phone.

Step 1 — Get the Tools and Packages

Download the package repository from the actively maintained GitHub project: https://github.com/HikariCalyx/w10m_oup (Windows 10 Mobile Offline Update Project V5.2, MIT-licensed, maintained by hikari_calyx).
The companion walkthrough and community discussion/support thread — including the original iutool.7z attachment and the newer semi-automated HCTSW_WXMSOUP tool — lives on XDA: https://xdaforums.com/t/guide-win10-mobile-semi-offline-update-project-10586-107-updated-v5-3-beta6.3527340/
Extract everything with 7-Zip. You’ll end up with two kinds of assets:
- Tooling binaries — iutool.exe (and, for later builds, getdulogs.exe).
- Package folders, organized by device “generation” and screen resolution/chipset.
Pick the correct folder for your phone (see the table below), and copy only that folder’s .cab files into a short path on your C: or D: drive, e.g. C:\W10MPackages. Do not extract or mix in .cab files from other device folders.

Device → Package Folder Map

Devices	Folder
Lumia 52X, 62X, 720/T, 810, 820, 822, Huawei Ascend W2	`2nd Generation\480x800`
Lumia 1320	`2nd Generation\720x1280`
Lumia 920/T, 925/T, 928, 1020	`2nd Generation\768x1280`
Lumia 1520	`2nd Generation\1520`
Samsung ATIV S / ATIV S Neo	`2nd Generation\I8750`
Lumia 43X / 532	`3rd Generation\43X-532`
Lumia 535	`3rd Generation\535`
Lumia 63X	`3rd Generation\63X`
Lumia 73X	`3rd Generation\73X`
Lumia 830	`3rd Generation\830`
Lumia 929 Icon / 930, Samsung ATIV SE	`3rd Generation\929-930-ATIVSE`
Lumia McLaren/Goldfinger	`3rd Generation\McLaren-Goldfinger`
HTC One M8 for Windows (AT&T)	`3rd Generation\M8ATT`
HTC One M8 for Windows (Verizon)	`3rd Generation\M8Verizon`
HTC One M8 for Windows (T-Mobile)	`3rd Generation\M8TMobile`
Lumia 540, TrekStor WinPhone 4.7	`4th Generation\540`
Lumia 640 / 640 XL	`4th Generation\640-XL`
LG Lancet VW820	`4th Generation\VW820`
BLU WIN HD/LTE, MCJ Madosma Q501	`4th Generation\BLUWINHDLTE-MADOSMAQ501`
Micromax W092	`4th Generation\MICROMAXW092`
Micromax W121, BLU WIN HD, RAMOS Q7	`4th Generation\MICROMAXW121-BLUWINHD-RAMOSQ7`

Step 2 — Connect the Device

Make sure the phone shows in Settings → Update & Security → For Developers with Developer Mode on.
Plug the phone into a rear USB 2.0 port with a reliable cable.
If Windows shows any driver error, or the device previously paired oddly: open Control Panel → Devices and Printers, right-click the phone, and choose Remove device. Reconnect it and let Windows re-enumerate it before continuing.

Step 3 — Run `iutool`

Open Command Prompt as Administrator (search “cmd” in Start, right-click → Run as administrator).

Change directory to wherever you extracted iutool.exe:

cd C:\Path\To\Your\Extracted\IUTool\Folder

Confirm the tool can see exactly one connected device:
```
1
iutool -l
```
(Note: that’s a lowercase L, not the digit 1.) This should print an identifier string for your phone. If it returns blank or errors, redo the “Remove device” step above and reconnect.
Push the package folder you isolated in Step 1:
```
1
iutool -V -p "C:\W10MPackages"
```
(Substitute your actual path, e.g. D:\480x800.) Do not disconnect the phone during this transfer.

You may see benign errors during transfer (e.g. “System cannot find the file specified” for MMOS-related files, or code 0x8024a000/8024a110) — both sources note these are expected and simply mean the device has taken over and is proceeding on its own.

Step 4 — Let the Phone Finish

The command prompt will show transfer progress, then a completion message (something like “Update Started”).
Unplug the phone and put it on charge.
Within roughly 5–10 minutes, check Settings → Update & Security → Phone Update — you should see an update actively installing.
The phone will show its “gears” spinning-update screen, reboot, and land on the Windows 10 Mobile 10586.107 out-of-box setup. The full process can take up to ~40 minutes.

Step 5 — Fix the Keyboard (if needed)

If your phone’s pre-installed language wasn’t English (US) or Simplified Chinese, the on-screen keyboard commonly stops working after the flash. To fix it:

In Settings → Time & Language → Keyboard, add the English (United States) keyboard, then remove any other keyboards.
Reconnect the (still-unlocked) phone to the PC.
Get the matching language .cab (referred to as Keyboard.cab / the “Internal IME Fix Package,” keyed by locale code — e.g. en-gb, en-in, fr-fr, ja-jp, zh-hk; see the XDA thread for the full code list and the attached fix package).

From an elevated Command Prompt in the iutool folder:

iutool -V -p "D:\Keyboard.cab"

Expect a benign error (code 8024a110) — the phone will still reboot and finish applying the fix. After that, the keyboard should work normally.

Step 6 — Post-Flash Cleanup (Recommended)

Because the offline method layers new files onto an old on-device database, the registry can be inconsistent right after the flash:

Go to Settings → System → About.
Choose Reset your phone.
Let it complete a full factory reset — this clears the old cache/temp state and stabilizes the new Windows 10 Mobile install.

Step 7 — Getting Further Updates (10586.107 → RS1 → RS2)

Once on the initial 10586.107 build, later Windows 10 Mobile builds (Anniversary Update “RS1”/14393, Creators Update “RS2”/15063) can be pulled the same way, but this stage genuinely requires internet access (a few GB of downloads) and a bit more manual curation:

On a PC with an internet connection, use a download manager (the Bengali source recommends Firefox + the “DownThemAll” extension) to bulk-download the relevant build’s .cab packages from Microsoft’s public update catalog mirrors linked in the XDA thread.
From the iutool/getdulogs folder on an elevated Command Prompt, capture your phone’s installed-package manifest:
```
1
getdulogs -o D:\my.cab
```
Open the resulting my.cab (7-Zip/WinRAR), extract InstalledPackages.csv, and open it in a text editor. Remove lines containing Nokia, OEM, and Qualcomm — these are device-specific packages you don’t need to re-push.
Use PowerShell (run as Administrator, Set-ExecutionPolicy Unrestricted) with a small script that cross-references your trimmed CSV against the downloaded build folder, copying only the .cab files your phone actually needs into a fresh folder (e.g. D:\RS1).

Push that curated folder the same way as Step 3:

iutool -V -p D:\RS1

Repeat the same process pointed at the RS2 package set once RS1 is successfully installed.

Simpler alternative for this stage: the newer semi-automated tool from the XDA thread (HCTSW_WXMSOUP, run via run_en.cmd) automates the getdulogs capture, package matching, and download steps described above — it’s the actively maintained successor to the fully manual process and is generally easier to follow than hand-curating CSVs and PowerShell scripts.

Notes on Discrepancies Between the Two Sources

Supported-device lists match across both sources and the current GitHub README, with one exception: an XDA forum commenter (ca_guri01) corrected the OP that the Lumia 520/520T/521 actually have 8 GB ROM, not 4 GB, and so are not excluded by the 4 GB ROM limitation — only the 530 and similarly capacity-limited devices are excluded.
If you hit an install error partway through, don’t disconnect the phone — run getdulogs -o 123.cab to capture a log bundle you can inspect (ImgUpd.log inside) or share when asking for help on the XDA thread.