How to merge JW Library backups from two devices
Combine the notes, highlights, bookmarks and tags from two or more JW Library backups into one .jwlibrary file — free, private, in your browser.
You studied the Watchtower on your phone and a different article on your tablet. Both devices now hold work the other does not — and JW Library cannot reconcile them. Its Restore is a full swap, not a merge, so whichever backup you restore deletes the other device's study. Using the app alone there is no way to end up with both.
That is what this site is for. It reads two (or more) .jwlibrary backup files and combines the notes, highlights, bookmarks and tags from all of them into one new backup — so nothing has to be chosen between. The merge runs entirely in your browser; your files are never uploaded to any server, so your personal study notes stay private.
It is also why the habit is preventive rather than remedial: once you merge periodically, you stop having to remember to restore before studying somewhere else. Study wherever you are, merge when it suits you, and every device catches up.
Step by step
Create a backup on each device
In JW Library, open Personal Study, tap the three-dot menu, choose Backup and Restore, then Create a backup. Do this on every device. Each one produces a .jwlibrary file.
Open JW Sync
Go to jwsync.org in any browser — on your phone, tablet or computer. Nothing to install.
Load both backup files
Drop in (or pick) the .jwlibrary files. JW Sync reads them locally on your device.
Review the pre-merge preview
Before anything is written, a preview shows exactly what will be combined. If the same note was edited differently on each device, the Conflict Reviewer shows both versions side by side with a word-level diff so you choose which to keep — or let “Suggest best” pick for you.
Download the merged file and restore it
Download the merged .jwlibrary file, then restore it on each device via Backup and Restore → Restore. Both devices now carry the complete, combined library.
What gets merged?
Notes, highlights, bookmarks, tags and their connections. Duplicates are detected automatically, so restoring the merged file never doubles anything up. Backups from Android, iPhone, iPad and the Windows app all use the same format and merge together freely.
Is it safe?
The merge never modifies your original files — it produces a brand-new backup, so your originals remain untouched as a fallback. And because everything runs client-side in the browser, no data leaves your device.
What is actually inside a .jwlibrary file
A .jwlibrary backup is a ZIP archive. Rename a copy to .zip and open it and you will find userData.db — a SQLite database holding every note, highlight, bookmark and tag you have ever made — alongside a small manifest.json describing the backup. Your notes live in a Note table, your highlights in UserMark and BlockRange, your bookmarks in Bookmark, and your tags in Tag and TagMap. Understanding that the backup is a complete database, not a set of loose files, explains everything else on this page: it is why a restore is all-or-nothing, and why two backups can be combined at all.
Why JW Library's own Restore cannot merge
When you restore, JW Library does not read your backup and add the missing items to what is already on the device. It replaces the device's database with the one from the file. That is a deliberate, safe design — it guarantees the device ends up in a known state — but it means restoring your tablet's backup onto your phone discards everything the phone had that the tablet did not. There is no setting to change this, which is exactly the gap a merge fills: it produces a single file that already contains both devices' work, so whichever device you restore it to ends up complete.
How duplicates are detected
Every note, highlight and bookmark carries a GUID — a unique identifier assigned when you create it and preserved in every backup thereafter. When the same item appears in two backups, both copies carry the same GUID, so it is recognised as one item and kept once. This is why merging the same pair of files twice does not double anything up, and why you can safely re-merge every week. Where the GUIDs match but the text differs — the same note edited on both devices — the item cannot be resolved automatically, so it is surfaced in the Conflict Reviewer with a word-level diff for you to choose.
What is not in the backup
A backup carries your personal study data only. Downloaded publications, Bible translations, videos and audio are not included, which is why backup files are small — usually a few megabytes even for a library built over years. After restoring on a new device you may need to download the publications you read regularly again. Nothing you wrote is affected by that; notes are anchored to publications by reference, so they reattach as soon as the publication is present.
If the merge reports 0 notes added
This is almost always correct rather than a fault. It means every note in the second file already existed in the first — common when you have merged recently, or when one device is simply behind the other. Check the pre-merge preview: it lists what each file contributes before anything is written. If you expected new items and see none, confirm you backed the device up after the study session you are looking for, since a backup only ever contains what existed at the moment it was created.
Frequently asked questions
- Can I merge more than two backups?
- Yes — load as many .jwlibrary files as you have devices. They are all combined into a single merged backup.
- Will merging create duplicate notes?
- No. Identical notes, highlights and bookmarks are detected and kept once. Genuinely different versions of the same note are surfaced in the Conflict Reviewer for you to decide.
- Does it work between Android and iPhone?
- Yes. The .jwlibrary format is identical across Android, iOS, iPadOS and Windows, so backups from different platforms merge without any conversion.
- Do I need to merge in a particular order?
- No. The merge is order-independent — the same set of files produces the same result whichever one you load first. The only thing order affects is which file is treated as the base for the preview's summary.
- What happens to tags that exist on only one device?
- They are carried across intact, along with the links between tags and the notes they mark. If both devices have a tag with the same name, it is treated as one tag and the notes from both are attached to it.
- How large is the merged file?
- About the size of the two originals combined, minus the duplicates — typically still only a few megabytes. Backups contain no publication media, so even a heavily annotated library stays small enough to email.
- Can I undo a restore?
- Not from inside JW Library, which is why keeping your original backups matters. The merge never modifies the files you load, so your pre-merge backups remain exactly as they were and can be restored if you want to go back.