Welcome to [i]PC-Phone USB Sync[/i] — local, cloud-free backup and sync.

This tab is an in-app overview that covers the essentials needed to use this app well.  In it, you'll find the following main sections:

— Introducing This App
— Usage Basics
— Running Content Backups
— Running Device Syncs
— Storage Choices
— More Essentials

For a restyled HTML version of this tab's content, visit the online Usage Overview of the User Guide by tapping the Docs button below.  For logistics info, open the About tab in this app.




[H1]Introducing This App[/H1]

This free and ad-free app makes content folders the same on your PCs, phones, and removable drives.  Compared to other tools, it's:

— Much quicker than full [i]copies[/i] because it updates content folders only for changes

— Faster and more secure than [i]clouds[/i] because it uses your local drives instead of networks and remote servers

— A cross-device solution for your content because it runs the [i]same[/i] on your phones, tablets, and PCs

This app brings PC-level tools to all your devices.  The content it manages isn't just contacts, calendars, and a few stray photos.  It's an entire [i]folder[/i] of your choice, including all its subfolders, photos, documents, music, and other media you value.

By using this app with a removable drive, you can both [i]back up[/i] this content on your phone or PC to save it, and [i]sync[/i] (a.k.a. mirror) it between your devices to make it match: from PC to phone, from phone to PC, and any other way you find useful.  Among its roles, this lets you:

— Use your [i]phone[/i] as a backup device on which you can view and modify saved content

— Switch your content-creation [i]tasks[/i] to a different PC or phone with a fast sync

— Sync your camera's new [i]photos[/i] to your PC or phone over a direct USB connection

— Ensure that your content copies are valid by [i]verifying[/i] them with this app

— Or simply [i]back up[/i] your phone or PC content to a removable drive for safekeeping 

In tech terms, this app's syncs are on-demand and one-way at a time; this keeps you in control and avoids lossy conflicts.  They can also be run in any direction and modify just the items you've changed; this makes them flexible and faster and gentler on your drives than simple copies.

Perhaps best of all, this app uses your USB ports and removable drives for its backups and syncs to avoid both slow networks and the privacy perils of clouds.  With this app, your stuff remains [i]your[/i] stuff, not someone else's point of control.

To use this app, get it's Android version at the Play store, and fetch its PC versions for Windows, macOS, and Linux at quixotely.com.  For most roles, you'll also need a removable drive to store and transfer content.  An SSD or thumb drive attached by USB is common, but microSD cards, cameras, and other devices work in this app too.




[H1]Usage Basics[/H1]

This section provides a quick review of this app's usage model.  Later sections go into more detail on specific usage modes, but the basics introduced here are straightforward.  Covered here:

— Definitions
— Requirements
— How to Use
— How to Run



[H2]Definitions[/H2]

Before we jump into syncs, let's cover a few preliminaries.  First off is terminology.  In this app and this doc:

— [i]Content[/i] is an entire folder (a.k.a. directory) and includes all the files of any sort and subfolders of any depth stored in that folder

— [i]Syncs[/i] propagate changes from one content folder to another on your request and are used for both content backups and device syncs

— [i]USB[/i] for brevity often means any sort of removable drive and may include microSD cards and other media in some contexts

— [i]PC[/i] stands for any Windows, macOS, or Linux computer running a supported OS version

— [i]Phone[/i] means any device running Android 8 or later, including foldables and tablets



[H2]Requirements[/H2]

Next up, to use this app, you'll need to set up a drive and one or more versions of the app itself.  Specifically, this app's usage requirements vary per your goals:

— To use this [i]app[/i], you'll need a removable drive (e.g., a portable SSD connected by USB) to host backups and/or serve as a conduit for cross-device content transfers.

— To sync to or from [i]phones[/i], you'll need both the Android app and a phone that supports removable drives with a USB port or otherwise (nearly all do today).

— To sync to or from [i]PCs[/i], you'll need one of the versions of this app for each type of PC you wish to use (e.g., Windows).

For example, to sync your PC to or from a phone, get the Android app, the version of this app for your PC, and a USB drive.  To back up content only, get the app for your device plus a USB drive.

For best results, removable drives used in this app should generally be formatted with the portable [i]exFAT[/i] filesystem.  All PCs and most phones support exFAT today, and most drives come preformatted with it.  FAT32 has timestamp limitations that can trigger spurious syncs when your devices' time changes, and other filesystems are not as portable.  See the web for formatting tips and "Why exFAT?" in Tech Notes for more info (tap Docs below).

Naturally, all the devices to which you'll be syncing — USB drives, phones, and PCs — must have enough free storage space to hold a copy of your content folder (or folders, if you'll sync more than one).  Most phones come with space to spare today, but bigger is better for content storage.

[i][color=YELLOW]Important[/color][/i]: while this app supports other types of storage covered in "Storage Choices" ahead, it cannot be used by [i]directly connecting[/i] a phone and PC by USB cable.  That mode runs MTP, a narrow protocol that is notoriously slow, lacks crucial utility, grants visibility only to PCs, and does not by itself mount drives as required by this app.  This app uses an intermediate drive to transfer content between devices, as the next section explains. 



[H2]How to Use[/H2]

With those preliminaries in hand, we're ready to explore content syncs.  Let's start with the general model first; it's simpler than the full details may suggest.

When using this app, you'll first collect your content files in a folder (or folders) using your local file explorer or other tool, and copy it to all your devices with this app's COPY.  Use subfolders to organize your content as desired; everything in your folder will be synced in full.

After the initial copies, you'll make changes on one device at a time, and propagate them to other devices with this app whenever you wish.  These change propagations (a.k.a. syncs) use your USB ports and removable drive, along with a [i][b][color=ORANGE]push[/color][/b][/i]/[i][b][color=ORANGE]pull[/color][/b][/i] model that varies by usage mode:

— To [i]back up[/i] your content on phones or PCs, you'll run this app's SYNC once: to [i][b][color=ORANGE]push[/color][/b][/i] changes from your device to USB. This leaves a mirror image of your content folder on your USB drive.

— To [i]sync[/i] your content between a phone and PC, you'll run this app's SYNC twice: to [i][b][color=ORANGE]push[/color][/b][/i] changes to USB on the source, and then to [i][b][color=ORANGE]pull[/color][/b][/i] changes from USB on the destination. This leaves a mirror image of your content folder on your phone, PC, and USB drive.

— To [i]sync[/i] your content between many devices, you'll run the app's SYNC N times for N devices: once to [i][b][color=ORANGE]push[/color][/b][/i] from the device with changes to your USB drive, and then once to [i][b][color=ORANGE]pull[/color][/b][/i] from your USB drive on each of your other devices. This leaves a mirror image of your content folder on all your devices as well as your USB drive.
 
In all modes, this app supports automatic [i]rollbacks[/i] (i.e., undos) for all the changes its syncs make on each device.  This helps ensure the safety of your content.  You can even undo multiple syncs to reset your content to a prior state in the past.  

Beyond copies and syncs, this app also has tools for verifying the content copies you'll create, along with portability utilities, configuration options, and help resources.  We'll explore these later.



[H2]How to Run[/H2]

Finally, you'll implement the preceding section's model by running actions in the app, but this is similarly simple.  All of the app's primary actions live on its Main tab; to run any one of them:

1) Tap the [color=BLUE]blue[/color] FROM and TO buttons in the Main tab to select content folders

2) Tap the [color=RED]red[/color] storage-type buttons in the resulting popups to find and pick folders

3) Tap the [color=GREEN]green[/color] action-name button in the Main tab to process your chosen folders 

You can often skip right to step 3 because the app remembers your prior choices.  Each action opens a popup to explain what it will do, remind you of your folder picks, and confirm its run.  Main-tab actions all launch operations in the open-source [i]Mergeall[/i] system, which is included with the app and can be explored with its link in the About tab.

To monitor an action's progress and results, inspect its [i]logfile[/i] in the Logs tab: pick a file there, and click a [color=GREEN]green[/color] action button to view.  TAIL shows the selected file's end, WATCH samples the logfile of the running action every second, and OPEN and EXPLORE open the selected file and the logfiles folder in your local viewers.  

For ease, the Logs tab automatically selects and scrolls to the most-recent logfile at the top of its date-sorted list when opened.  You can also use double and triple [i]taps[/i] on logfile names in Logs to run TAIL and TAIL+OPEN, respectively; a [i]splitter[/i] allows you to resize the logfile viewing area; and the popup shown on action exit includes brief logfile [i]summary[/i] info that's often enough. 

Logfile reports are straightforward and include [i]indicator[/i] lines at the end if there are any messages that warrant investigation (popup summaries show indicators too).  If you see an indicator line, search logfiles for "*" to locate errors and notes, and see Tech Notes in this app's User Guide for more about logfiles in general (tap Docs below).

Although it supports a variety of actions, this app's main tool is the SYNC button on its Main tab.  This makes a TO folder the same as a FROM folder quickly, by updating TO only for changes made in FROM.  SYNCs detect changes by checking timestamps, sizes, and folder structure, to avoid slower full copies.  They can also be rolled back with UNDO if needed.

The way you'll use SYNC depends on whether you want to back up your content, sync it between PCs and phones, or both.  The next two sections provide step-by-step coverage of both usage modes.




[H1]Running Content Backups[/H1]

To use this app to back up content folders on your PC or phone, you'll need a removable USB drive to host the backup copy and versions of this app for each device you'll be backing up.  Get the Android version for your phones and one of the versions of this app for your Windows, macOS, or Linux PCs.

See "Requirements" above for tips on the USB drive, and tap the Downloads link in the About tab to fetch both Android and PC versions of this app.  For backups, you'll copy content first, sync it later after changes, and verify it as desired, as the following sections will explain:

— Initial Copy
— Backups
— Verify and Restore



[H2]Initial Copy[/H2]

To get started, run an initial content-folder copy from your PC or phone to your USB drive, by selecting folders and using the app's COPY button once:

1) Attach your USB drive to your PC or phone

2) Select your PC or phone folder as FROM and a USB-drive folder as TO

3) Run the app's COPY

In step 2, you're choosing a folder on your USB drive to host the content copy: FROM's content folder is added to TO as a new [i]subfolder[/i].  This first copy may be slow because it must copy your content in full, but later backups will be fast.



[H2]Backups[/H2]

Thereafter, whenever you want to update your backup copy, run SYNC just once, with the PC's or phone's content copy as FROM, and the USB drive's copy as TO:

1) Attach your USB drive to your PC or phone

2) Select your PC or phone folder as FROM and your USB-drive folder as TO

3) Run the app's SYNC

In step 2, you're choosing existing content-copy folders.  Every time you run all three steps, your backup drive's content copy will be made the same as your device's copy. 

These updates will be fast because they change your USB drive's copy only for changes you've made on your PC or phone.  Moreover, because the app remembers your FROM and TO settings between runs, you'll normally need to just attach your drive and press SYNC.

Keep in mind that the app's SYNC button is used for both content backups and device syncs.  Here, it makes a backup copy the same as a live copy quickly and works as a backup tool.  Device syncs ahead will use it as a more general change-propagation tool.



[H2]Verify and Restore[/H2]

To verify that your backup copy matches your device, attach your USB drive to your device and select as above, then run either SHOW or DIFF in the app.  SHOW runs a fast timestamp-based comparison of FROM and TO; DIFF runs a complete byte-for-byte comparison but is much slower because of this and should be used only occasionally.

To restore your content from a backup, simply select the USB drive's content copy as FROM and your device as TO, and either SYNC to an existing copy or COPY the USB drive's copy in full.  Once restored, you can SYNC to your USB drive again to back up when desired.

Note that the UNDO button can roll back changes made to your USB drive's copy by a SYNC but is rarely useful in backups mode.  Also note that if you opt to sync PC and phone devices, your USB drive will automatically serve as a backup copy of your content, and no extra backup steps are required.  To see how, we have to move on to the next section.




[H1]Running Device Syncs[/H1]

To use this app to sync content folders between PCs and phones, you'll need a removable USB drive to serve as a go-between for syncs and versions of this app for each device you'll be syncing.  Get the Android version for your phones and one of the versions of this app for your Windows, macOS, or Linux PCs.  See "Requirements" above for USB-drive tips and tap the Downloads link in the About tab to fetch Android and PC versions of this app.

Device syncs always update a destination device to match a source device, but they can run in any direction.  For instance, they can be run from PC to phone, from phone to PC, or between any combination of PCs and phones, and you need PC versions of this app only if there are PCs in the mix.  Here, we'll focus on typical PC/phone syncs.

Device syncs also use an intermediate USB drive to propagate content and changes between your devices.  This just means you'll run the app twice: once on the source to push to the USB drive, and then again on the destination to pull from the USB drive.  In effect, your drive plays the same role as a remote server in cloud storage but faster and safer.

By syncing to and from a go-between USB drive this way, your content copies on your PC and phone are made the same without being directly connected and without compromising privacy.  As a bonus, your USB drive becomes an extra backup copy of your content.

The following sections detail the steps you'll run to copy your content initially, sync it for changes later, and verify your content copies as desired:

— Initial Copy
— PC-to-Phone Syncs
— Phone-to-PC Syncs
— Verify, Restore, and Undo
— Other Sync Modes



[H2]Initial Copy[/H2]

Let's assume for now that your content lives on your PC initially.  To get started, perform an initial content-folder copy from your PC to your phone using your USB drive as a go-between and running the Main tab's COPY on each device:


1) [b][i]On your PC:[/i][/b]

a. Attach your USB drive

b. Select your PC's folder as FROM and a USB drive folder as TO

c. Run the app's COPY


2) [b][i]On your phone:[/i][/b]

a. Attach your USB drive

b. Select your USB drive's folder as FROM and a phone folder as TO

c. Run the app's COPY


In both selection steps, you're choosing a folder on the destination to host the content copy: FROM's content folder is added to TO as a new [i]subfolder[/i].  If your content instead lives on your phone initially, do the same as above, but swap PC and phone roles: copy from phone to USB on your phone, then from USB to PC on your PC.  

Either way, the net result makes your content folder the same on your PC, phone, and USB drive.  This first copy may be slow because it has to perform a full byte-for-byte copy, but later syncs will be much faster because they'll update TO only for changes in FROM.



[H2]PC-to-Phone Syncs[/H2]

After the initial copy, whenever you want to update your devices' content copies to be the same, run SYNC twice: once on the source device to sync to the USB drive, and then again on the destination device to sync from the USB drive.

For example, to sync your phone's content copy to reflect changes made in your PC's content copy, simply run SYNC on each device with the USB drive in between:


1) [b][i]On your PC:[/i][/b]

a. Attach your USB drive

b. Select your PC's folder as FROM and your USB drive's folder as TO

c. Run the app's SYNC


2) [b][i]On your phone:[/i][/b]

a. Attach your USB drive

b. Select your USB drive's folder as FROM and your phone's folder as TO

c. Run the app's SYNC


In both selection steps, you're choosing existing content-copy folders.  Every time you run this procedure, it updates your phone for changes made on your PC and makes your content copies the same again on your PC, USB drive, and phone.

Just as in backups, because this app automatically remembers the FROM and TO paths you used for prior runs on each device, the selection steps above aren't required for later runs if you sync the same way each time: on both PC and phone, simply attach your USB drive and press SYNC.



[H2]Phone-to-PC Syncs[/H2]

Likewise, to sync your PC's content copy to reflect changes made in your phone's content copy, simply run SYNC on each device with the USB drive in the middle:


1) [b][i]On your phone:[/i][/b]

a. Attach your USB drive

b. Select your phone's folder as FROM and your USB drive's folder as TO

c. Run the app's SYNC


2) [b][i]On your PC:[/i][/b]

a. Attach your USB drive

b. Select your USB drive's folder as FROM and your PC's folder as TO

c. Run the app's SYNC


Just like PC-to-phone syncs, you're choosing existing content-copy folders in both selection steps, and your content copies on your phone, USB drive, and PC are made the same again every time you run this.  And here too, the selection steps above can often be skipped because FROM and TO paths are saved on both your phone and your PC: just attach USB drive and SYNC on both devices to repeat prior syncs.



[H2]Verify, Restore, and Undo[/H2]

To verify that your device copies are the same, first verify your USB drive's copy to one device, then verify it to the other.  If the USB drive's copy matches both devices, then the device copies are the same too (abstractly speaking: if [b][color=ORANGE]A = B[/color][/b] and [b][color=ORANGE]B = C[/color][/b] then [b][color=ORANGE]A = C[/color][/b]).

More concretely, to verify that your content copies match, attach your USB drive to your device, select one copy as FROM and the other as TO (the direction doesn't matter here), and run either SHOW or DIFF in the app.  SHOW runs a fast timestamp-based comparison of FROM and TO; DIFF runs a complete byte-for-byte comparison but is much slower because of it and should be used only occasionally.

Also note that because your USB drive will always store an extra backup copy of your content, you can use it at any time to restore your PC, phone, or both: just run the app with your USB drive as FROM and your device as TO, and either SYNC (if the device's copy is usable) or COPY (to copy the content folder to the device in full and anew).

Finally, the app's UNDO button allows you to roll back all the changes made to any TO by the most recent SYNC run against it.  This is a last-resort safety mechanism which you can use when syncs go awry, and it fully restores TO to its pre-SYNC state.  Though more rarely needed, you can also undo multiple SYNCs one at a time with multiple UNDOs: each one resets the TO folder to its state further in the past.  

[i][color=YELLOW]Important[/color][/i]: UNDO works only if backups are enabled in the Config tab, which makes SYNC save changed items in TO's __bkp__ folder.  This is enabled by default and should generally be left this way; disabling SYNC backups can save some space and runtime, but it means that SYNC changes are permanent.  Mod with care.



[H2]Other Sync Modes[/H2]

Besides syncing between a phone and a PC per the last two sections, this app can also be used to sync between two or more phones, two or more PCs, or an [i]arbitrary mix[/i] of phones and PCs.  These modes work like those already detailed: simply SYNC from the source device with changes to your USB drive, and then SYNC from your USB drive to one or more destination devices.

It's also possible to use this app to separately sync [i]subfolders[/i], and this provides a way to change content on multiple devices between syncs, as covered in "Changes" ahead.  This app can even be used to sync to or from a [i]camera[/i] attached directly to a phone or PC, as discussed in the following section.




[H1]Storage Choices[/H1]

To use this app, organize the content files you wish to back up or sync into folders as noted earlier (see Usage Basics).  You can create and sync multiple content folders, but it's usually easier and quicker to use just one for all your content, or at least one for content that's prone to change.  Use subfolders in your main folder to organize content by types, and sync either the main folder or individual subfolders.

You'll also need to choose a location to host your content folder on each device.  The Main tab's folder choosers, opened by its [color=BLUE]blue[/color] buttons, allow you to pick folders in on-PC, on-phone, and removable-drive storage.  Storage types are called out by label or other ID in the [color=RED]red[/color] radio buttons at the top of the chooser popup: scroll to see all of your storage types, and tap to go to a type's root folder at any time.

Once you've selected a storage type, you'll navigate among its folders much like you would in a file explorer: double-tap to open a folder, single-tap to select, use "../" or "..\" to go up one level, and toggle between icon and list views with the chooser's [color=GRAY]gray[/color] buttons.  Your icon-or-list view preference can also be made permanent in the Config tab.

You can store your content nearly anywhere in any storage type, but it must be accessible to this app as well as file explorers and programs you'll use for content views and changes.  The following sections provide tips on storage options per device type:

— PC Storage
— Android Storage 
— USB-Drive Storage
— Storage on Other Media
— Storage Special Cases



[H2]PC Storage[/H2]

Internal on-PC storage generally means your home holder, but it can be almost anywhere in your device's system drive.  The app's folder choosers label these as PC and ROOT:


[color=RED]PC[/color]

This is your [i]home folder[/i] of your user account on your PC.  Choosers label this as PC because it's the normal and recommended location for creating and hosting your content folder.  Anywhere goes here, though top-level folders make selections easier.


[color=RED]ROOT[/color]

This is the root of the entire [i]system drive[/i] on your PC.  It's usually "C:" on Windows and "/" on macOS and Linux.  It gives access to everything on the drive, including your home (PC) folder, though some parts of ROOT may not be usable due to permission rules; see your platform for details.

On Unix PCs (macOS and Linux), ROOT also gives access to mounted drives' folders that do not appear in choosers due to atypical mounts (more on this below).  Because PC is usually a better choice for content, ROOT can be disabled in the Config tab if unused.


[b][i]Others[/i][/b]

On Linux PCS, choosers may also show an [color=RED]OS[/color] for the mounted [i]Windows drive[/i] on dual-boot setups, and Windows PCs may also show WSL2's [i]Linux drive[/i] as a [color=RED](Remote)[/color] storage because it uses a network protocol.  Remote storage is covered ahead, and the User Guide's Tech Notes explores using this app in WSL2.  Removable drives and other external media also appear in folder choosers on PCs as described ahead.



[H2]Android Storage[/H2]

Internal on-phone storage comes in multiple flavors, with differing access rules and longevity.  The most useful of these are made available as PHONE and APP in the Main tab's choosers:


[color=RED]PHONE[/color]

This is [i]shared storage[/i] on your phone.  It is broadly accessible to file explorers and apps, never automatically deleted, and generally recommended for your content.  You can make your content folders anywhere in this storage, though its top level yields simpler paths and faster selections.


[color=RED]APP[/color]

This is this app's [i]app-specific[/i] (a.k.a. external private) storage on your phone.  It can host your content folders too and today is accessible to most file explorers and much faster than shared storage in some usage modes (10x faster is not unusual).

In the minus column, APP will likely grow less accessible in future Androids.  Worse, it is automatically deleted if you either clear this app's data in Settings or uninstall this app without opting to retain its storage in the uninstall dialog.  Please use APP with care; it can be disabled in the Config tab if you use only PHONE storage.

[i]Update[/i]: in 2025, file-explorer access to content stored in the APP folder has diminished.  As tested, [i]Cx[/i] still works, some apps refuse access, and others simply open Android's built-in explorer, including [i]Files[/i] not made by Google.  This may vary by device and time, so vet on your phone before using APP.


[b][i]Others[/i][/b]

Android can also display a [color=RED]ROOT[/color] for its root folder, but this requires a rooted phone to be useful and is presently experimental and disabled; enable it in the Config tab.  Apps also have [i]app-private[/i] (a.k.a. internal private) storage; because it can't be used by any other app, it has no valid roles for general content and is not shown in choosers.  Removable drives and other external media also appear in folder choosers on Android as described in the following sections.



[H2]USB-Drive Storage[/H2]

This category includes both SSDs and thumb drives attached by USB port.  On all platforms, your drive's name shows up at the top of the app's folder choosers (e.g., [color=RED]MYSSD[/color]).  This name comes from your drive's label, if set; if no label is available, the name is a serial number or generic title which depends on the host platform (more on this ahead).

If you attach more than one drive, each drive's name appears, and USB hubs work in this app on both PCs and Android.  Almost anywhere goes for content folders on such drives, though the drive's top level makes selections easier.  Exception: if you're using Android 10 or earlier, your options in this category are constrained; see the special case below.



[H2]Storage on Other Media[/H2]

In addition to PC, phone, and USB-drive storage, you can also select and use microSD cards, optical disks, network drives, and cameras as FROM or TO in this app, if the host device makes them accessible (technically, as mounted drives).  Generally, Android phones support microSD cards and cameras, and PCs support all four media types.  Here's a brief rundown on each.


[b][i]microSD[/i][/b]

If present, the names of microSD cards will appear alongside other storages in folder choosers.  On Android devices, such cards may be either embedded or attached, but embedded mode is increasingly rare and cannot match USB's convenience, and microSD in either mode is likely slower than other USB drives today (though express cards may narrow the gap, and some phones still have slow USB ports).


[b][i]Optical[/i][/b]

Optical storages, including attached BDR and CD-ROM disks, also show up in the app's folder choosers and are fully supported as content sources where available.  These storages are generally usable on all PCs, and they may be useful for accessing content copies burned to disks for comparisons or restores.


[b][i]Remote[/i][/b]

Remote storages, including network shares, virtual-machine access points, and WSL2 storage on Windows, are also listed in choosers and supported in full if present.  These storages work on PCs if mounted to a standard folder on Unix or mapped to a drive letter on Windows, though USB drives are generally recommended over networks for portability, speed, and privacy.


[b][i]Camera[/i][/b]

Finally, a camera connected by a USB cable to your phone or PC will also show up in this app's folder choosers, as long as the camera functions as a drive when connected this way.  Although cameras may not be suitable for general content storage, you might use this to copy over just new photos and remove deleted photos, by running a SYNC from your camera's DCIM folder to your phone or PC.



[H2]Storage Special Cases[/H2]

While the preceding covers most storage usage, there are three exceptions worth calling out here:


[b][i]Unlabeled drives[/i][/b]

For all drives, this app uses drive [i]volume labels[/i] for drive names in the red buttons at the top of folder choosers.  You can set this label to anything you like in most file explorers or disk managers.  If the label is not set, the app uses a name that varies by platform: Windows uses [color=RED](Removable)[/color] or [color=RED](Remote)[/color]; macOS uses [color=RED]Untitled[/color]; Linux uses the drive's unique numeric ID (a.k.a. serial number); and Android uses the device name.


[b][i]Atypical drive mounts[/i][/b]

The rules used by the app to populate its choosers with removable drives vary by platform: macOS looks for drives in "/Volumes," Linux checks "/media" and "/mnt," Windows inspects mapped drive letters, and Android tells the app where it has mounted drives.  These are the norms for each platform and generally work well. 

As a fallback option on Unix-based devices, you can also navigate to any drive's mount location from the ROOT folder, even if the drive is not called out at the top of folder choosers.  This generally applies only to atypical mounts on macOS and Linux; Windows has no system-wide root, and Android's system root is inaccessible on unrooted phones.


[b][i]Rules for removables on Androids 10 and earlier[/i][/b]

In this app, you can read and update any location on removable (e.g., USB and microSD) drives in Androids 11 and later.  On Androids 10 and earlier you can read from anywhere on removables too, but you can update such drives only in a folder specific to this app: Android/data/com.quixotely.usbsync.  Updates anywhere else on removable drives are not allowed by these older Androids.

In practical terms, this means that on Androids 10 and earlier, you should host content in this specific folder on removable drives if it will be either [i]backed up[/i] from your phone or [i]synced[/i] from your phone to your PC.  Content used only in PC-to-phone syncs need not follow this rule on older Androids because reads work everywhere, and Androids 11 and later have no such constraints.  Either way, this app will always warn you if you select an invalid removable folder for Main-tab actions that may modify it on older Androids.

See the User Guide's GUI-guide coverage of the Main tab's folder chooser for more info on this rule and storage in general.




[H1]More Essentials[/H1]

This last section dives deeper into additional topics that you'll find important as you start using this app.  Some of the topics here are covered further in other parts of this app's docs as noted along the way.  In this section, you'll learn about:

— Changes
— Configuration
— Portability
— Performance
— Permissions
— Privacy



[H2]Changes[/H2]

This app's syncs are one-way [i]mirrors[/i], which propagate changes from a source to a destination.  This requires that changes to a content folder are made on just one device at a time.  Otherwise, changes made in destination folders between syncs may be lost on the next sync.  The simplest way to meet this requirement is to designate one device as changeable, and sync its content copy to other devices before making changes on them. 

However, it is also possible to use this app to resolve changes made on [i]multiple[/i] devices between syncs.  To do so, changes on each device must be isolated in disjoint folders: make changes in a different folder or subfolder on each machine.  Then, to combine changes, sync the disjoint folders separately. 

For example, you might edit documents in one folder on device A and images in another folder on device B.  To make the devices the same later, sync the documents folder from device A to B and the images folder from device B to A.  This requires extra SYNC runs compared to syncing a single common folder, but it allows you to make isolated changes on different devices before a sync.

If you use this mode, be careful to avoid making changes in the [i]same[/i] folder on different devices, because the destination's changes would be erased by syncs.  Also, when changing [i]subfolders[/i] of a common root folder, sync backups should usually be disabled in the Config tab for subfolder syncs because backup folders in subfolders won't apply after syncs from the common root.

For more on the rationale for one-way syncs in this app, see "Manual Two-Way Syncs" in Docs' Tech Notes.



[H2]Configuration[/H2]

You can customize both the appearance and behavior of this app in a variety of ways in its Config tab.  This tab describes available settings, which are saved between app runs if you tap the tab's "Save Changes" button.  As noted earlier, the app also saves Main-tab FROM and TO paths automatically after an action run, so you don't need to reselect.  For finer-grained Config details, please see the GUI Guide in the User Guide (tap Docs below).

[i][b]Tip[/b][/i]: this app uses a default font size that may be subpar on some devices.  To change the size of all its text, mod Config's "Global font size."  This acts like a zoom in or out for text and generally works better in this app than your device's display settings.



[H2]Portability[/H2]

Although this app runs on both PCs and Android, some exotic content items may not be fully portable due to interoperability constraints on some devices.  The good news is that nearly all content consists of normal files and folders, which can always be processed by this app on all devices without loss or error.  If your content follows this norm, you can safely ignore most portability concerns.

Rarer items such as symlinks and Unix permissions, however, may not survive journeys through devices which cannot store them.  In this app, Unix [i]permissions[/i] are copied to the extent allowed by the destination, and [i]symlinks[/i] are skipped with logfile error messages when copied to devices that don't support them.  This rule applies to both the SYNC and COPY actions in the app.  

While some platforms (e.g., macOS) silently forge [i]symlinks[/i] with simple files, this hack can fail in some later usage contexts and would yield perpetual file-type differences if used by this app.  Your best option is to omit symlinks in content folders which may be copied to less-supportive devices.  For more info, see the User Guide's Tech Notes.

Some [i]filenames[/i] created on Unix (and some Android storage types) can't be stored on all devices either, but these can be automatically adjusted to be portable with the Main tab's NAME action.  For more details, please see the full User Guide's coverage of the NAME action, in its GUI guide; use this action's report-only option to check before changing.  

In addition, this app's Config tab includes an option, enabled by default, to skip [i]one-platform items[/i] that don't belong in cross-platform content (e.g., macOS ".DS_Store" and "._*" files and Windows "*Zone.Identifier" files); see the Config coverage in Docs' GUI Guide for more info.  Though rare and obscure, macOS's Unicode policies may also pose pitfalls for some filenames; see Tech Notes for coverage and fixes.  

[i][color=YELLOW]Important[/color][/i]: skipping one-platform items will skip all items whose names begin with a leading period (e.g., ".filename") on all platforms.  These items are hidden by Unix convention and are not normally intended to be part of a user's content collection.  If you wish to include such items, simply uncheck this toggle in the Config tab before running Main-tab actions.



[H2]Performance[/H2]

Main-tab actions are run one at a time; you can't start another until a running action finishes.  Once started, they never block the app's GUI, and always continue running if you navigate to another app on any host, pause the app with Back on Android, or encounter a blank screen due to timeout or power-button press on Android.  This means you can freely use other apps and turn off your screen without pausing a long-running action in progress.

The mode used to run actions varies by platform.  You can simply use the defaults and don't need to know about processes and threads to use this app.  Because you can choose modes on Android though, it may help to know the basic differences:

— On [i]PCs[/i], Main-tab actions run in parallel threads, which never pause if the GUI is minimized or loses focus and stop only if you close the app itself and confirm the close.  

— On [i]Android[/i], Main-tab actions by default run as foreground-service processes with notifications but can optionally be run as threads as on PCs.  Neither pauses the GUI and both stop only if you close the app with a Recents swipe.

Android foreground [i]services[/i] post a notification while running, to let you know when an action finishes.  Please allow notifications when prompted by recent Androids on the first action run.  On some phones, this mode may also minimize the odds of an app kill or stop for battery or memory management. 

Android [i]threads[/i] do not post notifications and are enabled by unchecking "Run Main actions..." in the Config tab.  They are forced on in Android 8 for implementation reasons but are otherwise not required.  Actions run similarly fast in both Android modes and as quick as equivalent commands in the [i]Termux[/i] app.  Threads, however, are a fallback option if a future Android limits or disallows foreground services for this app (e.g., Android 15+ adds a 6-hours/day time limit, though it doesn't impact this app in practice: see Tech Notes).

Also on Android, the [i]Back[/i] button or gesture returns to the Main tab from another tab but puts the app in paused mode when run on the Main tab.  In paused mode, the app's GUI is suspended but stays in memory, and any running Main-tab action keeps running.  With services, the action posts a notification to give status during the pause.  To unconditionally close the app and any running action, use a swipe on your phone's Recents (i.e., open apps) display.  

[i][color=YELLOW]Important[/color][/i]: closing the app on Android with a Recents swipe frees up the app's memory, but it also may harm your content and require action reruns if a Main-tab action other than SHOW or DIFF is in progress.  Before closes, check app status via its Main-tab image or Android notification if you are unsure if an action is running.  On PCs, normal closes trigger warnings if an action is running, but the same caution applies for forced closes.

[i][b]Tips[/b][/i]: on some Android devices, tapping or pressing the screen during a SYNC or other action may make the action run faster, subject to Android's processor-scheduling policies.  Some Android devices may also run actions quicker if the Logs tab's WATCH is turned on to monitor action output, though this is also subject to Android policies and does not help on most phones.

[i][b]See also[/b][/i]: consult the User Guide's App Packages for notes about Android memory, speed, and power, and browse its Tech Notes for more on Android app kills and stops.  The About tab also includes a note about Android battery optimizations; no issues are known and multi-hour runs for very large content work well, but you may need to change power settings for this app on some phones if its actions are killed or paused.



[H2]Permissions[/H2]

On Android, this app requests only:

— Notifications permission for services (per the prior section)

— General permission for storage on Androids 10 and earlier

— All-Files-Access permission for storage on Androids 11 and later

These last two of these allow the app to access your content folders stored in both on-phone shared storage and your removable drives.  Because these are crucial on Android, you'll be prompted to enable these permissions on the app's first run, as well as by folder choosers and Main-tab actions if not enabled.  You'll also be prompted to restart the app once after granting these permissions, where needed.

On Windows and Linux PCs, this app requires no storage permissions; you can store your content folders in any PC or USB-drive location that you have permission to access.  The same is generally true for macOS, but that platform has storage-access rules that are more convoluted and prone to change. 

Specifically, macOS will ask you to enable removable drives and certain folders when they are first accessed, and the app's first-run dialogs mention macOS's Full Disk Access permission as an option.  Full Disk Access may help the app use items considered sensitive by macOS, but it is not required for typical content folders.

Besides storage, some PCs may require you to give the app permission to run on its first launch.  This is a one-time step, described per platform in the User Guide's App Packages.

Regardless of permissions, this app never accesses any items on any platform unless you instruct it to do so.  Moreover, this app holds no Internet permissions and accesses the Internet only when you ask it to open its own online resources with an app of your choosing.



[H2]Privacy[/H2]

Please see this app's About tab or website for its privacy policy.  In short, privacy is a by-design feature of this app.  Its core purpose, after all, is to keep your content safe from the many privacy perils of cloud storage.




[H1]For More Info[/H1]

That brings this usage overview to a close.  You should now have the essentials needed to use this app well, but more resources are available to help you manage your content.

For this app's terms of use, privacy policy, downloads, and version, open the About tab.  For this app's website and your SYNC backups folder, tap Website and Backups below, respectively.  And for more usage info, visit the full online User Guide by tapping Docs below.