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diff --git a/docs/USERGUIDE.md b/docs/USERGUIDE.md
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+++ b/docs/USERGUIDE.md
@@ -372,12 +372,65 @@ is a folder**. Thumbnails come from the node, already rotated correctly. A
 photo opens full size, with a slideshow button that moves on every five
 seconds and stops at the album's last photo.
 
+A photo you uploaded can be deleted: right-click it, or use the bin in the bar
+above an open photo (the way in on a phone). The node's operator can delete any
+photo. Both ask first.
+
 **Location data is never shown.** Photos shows when a picture was taken and
 what took it, and no coordinates anywhere. Worth knowing, though: the
 coordinates are still inside the photo itself, as your phone wrote them, so
 anyone who downloads the original file has them. Strip them before sharing if
 that matters to you.
 
+### Backing up your phone's photos
+
+On the Android application, **Phone → Android Sync** in the side menu holds
+**Photo backup**, which sends the photos taken on your phone to a folder of one
+of your groups, once a day.
+
+- **Set up** asks for access to your photos, then for a group, a folder and the
+  albums to send. Only folders you may add to and that the group's Photos tab
+  shows are offered. The camera is ticked; screenshots and other albums are
+  yours to add.
+- By default **the photos already on the phone are sent too**, newest first,
+  then each new one. Choose "Only photos taken from now on" to skip the ones
+  already there.
+- Before anything is sent you are told where the photos go, how many members
+  the group has and how much will be sent. **Everyone in that group will be
+  able to see and download them.** You can delete what you sent afterwards,
+  but not the copies others have already downloaded — so pick the group with
+  care. Changing the group or the folder later asks again.
+- It runs **on Wi-Fi only** (more exactly, on a connection that is not charged
+  by the amount), once a day, while the application is open — with the screen
+  off too. If the application was not opened all day, it runs the next time it
+  is. **Back up now** runs at once; on mobile data it tells you how much it is
+  about to send and asks first.
+- Photos go into folders by year, then year and month (`2026/2026-10`). **A photo you delete
+  from the phone stays in the group**, and one deleted from the group is not
+  sent again, unless the application is reinstalled. A photo you edit on the phone is sent again beside the original,
+  with `-edited-` and the date in its name.
+- **Where a photo was taken is removed** from the copy that is sent.
+- If the backup cannot go on — the node's disk is full, the folder no longer
+  accepts files, you left the group — it stops, says why once in a
+  notification and on the Android Sync page, and tries again the next day.
+
+### Backing up your phone's contacts
+
+**Contacts backup**, on the same **Android Sync** page, sends a copy of your
+phone's contacts to a group, once a day when they have changed.
+
+- **Only a group you are the only member of** can receive it: your address
+  book is not something to share. If you have none, create a group just for
+  yourself first. If somebody joins that group later, the backup stops and
+  tells you.
+- You choose any folder of that group you may add to; the copies go into a
+  folder named after you inside it, such as `Backups/alice-contacts`.
+- Each copy is a `.vcf` file with the date in its name
+  (`contacts-2026-10-10-0900.vcf`). Any phone can import it. Older copies are
+  kept, nothing is ever replaced.
+- It runs on any connection, since a copy is small. **Back up now** sends one
+  at once if your contacts changed since the last copy.
+
 ### Search
 
 The magnifying glass in the sidebar searches **across every group you are in**
@@ -851,6 +904,9 @@ anything missing.
 **"No nodes are currently online for this group."**
 The node is not running, is not reachable, or has not linked its key to the
 hub. On the node: `meshbay-node status`, then Step 4 and 5 of the quickstart.
+In the desktop app, the **Node** page says when your account is linked to the
+node of another machine (**Link this node instead**); **Profile → Unlink**
+lets go of a node from anywhere, for a machine that is gone.
 
 **A member sees the group but no files.**
 They never redeemed an invitation code, or the group has no key
@@ -1030,6 +1086,12 @@ Better to know now than to go looking for it:
   with the screen off, from one track to the next, with a notification shown
   while it plays. A phone browser works too.
 - **A node cannot be hosted on Android**, and is not planned to be.
+- **Photo backup only runs while the application is open** (the screen may be
+  off). There is no button yet to remove everything the phone sent to a group
+  in one go — delete those files from the group instead.
+- **Photos in the HEIC format are backed up but do not show in Photos** yet:
+  they are in the folder (Files lists them) and can be downloaded. Most Android
+  phones take JPEG unless set otherwise.
 - **Hubs do not talk to each other yet.** Everyone in a group needs an account
   on the same hub.
 - **Casting reaches Chromecast devices** from the desktop and Android