How to merge JW Library backups from two phones

JW Library's own backup and restore feature moves one device's data to another — it doesn't combine two devices' data together. If you've been marking up publications on both your phone and a tablet, or switched phones without transferring first, JW Library alone can't merge those two histories. That's what a merge tool is for.

1. Export a backup from each device. In JW Library, go to Personal Study (or Settings), then Backup and Restore, then Create a Backup. Do this on every device whose notes you want combined.
2. Get all the backup files onto one device. Email them to yourself, use a cloud drive, or a cable — however's easiest to get every .jwlibrary file onto the phone or computer you'll use to do the merge.
3. Open JW Fusion and add all the files. Select or drag in every backup you exported. You need at least two.
4. Merge. JW Fusion reads each file locally in your browser and combines notes, highlights, bookmarks, tags, and playlists into one consolidated backup — nothing is uploaded anywhere in the process.
5. Restore the merged file on each device. In JW Library, go to Backup and Restore, then Restore a Backup, and select the merged file. Repeat on any device you want the combined data on.

A couple of things worth knowing before you start: overlapping highlights and duplicate notes are detected and merged rather than duplicated, and restoring replaces a device's current personal study data with what's in the backup — so restore the merged file on every device you want it on, not just one.