Edited metadata.db. What are the implications?

VelvetElvis · 02-07-2026, 07:01 PM

Edited the "books" table in metadata.db as a bandaid fix to the broken Calibre Sync app due to v9 changes. (I added back the "isbn" and lccn" columns)

Everything is working fine now, but what are the implications as far as Calibre is concerned? Will this database get rebuilt at some point by something I do? Am I safe to leave these 2 fields back in?

kovidgoyal · 02-07-2026, 08:21 PM

DO NOT mess with metadata.db you risk total data loss if you do. calibre sync has already released a beta simply use that or wait a few more days.

slm · 02-07-2026, 08:31 PM

Kovid is of course correct that you should not mess with metadata.db.
But his comment that messing up the database can cause complete data loss is saddening.

One of the most wonderful features of the early versions of Calibre was that everything could be reconstructed from the book folders themselves.

I'm not sure when Calibre lost that level of safety.

kovidgoyal · 02-07-2026, 09:04 PM

That works when metadata.db is corrupted and cant be opened, and continues to work to this day.

Once you start modifying metadata.db outside of calibre you can do pretty much anything including changing data and those changes will propagate to the distributed backups, leading to the above mentioned total data loss. Simply *never* modify metadata.db outside of calibre. metadata.db is *internal to calibre*. And calibre has *never* been robust against users messing with metadata.db directly and never will be.

PeterT · 02-07-2026, 09:47 PM

Quote:

Originally Posted by kovidgoyal

DO NOT mess with metadata.db you risk total data loss if you do. calibre sync has already released a beta simply use that or wait a few more days.

I believe Calibre Web has a beta. Calibre Sync on the other hand is MIA

Sent from my Pixel 9a using Tapatalk

VelvetElvis · 02-07-2026, 10:02 PM

Quote:

Originally Posted by kovidgoyal

DO NOT mess with metadata.db you risk total data loss if you do. calibre sync has already released a beta simply use that or wait a few more days.

Egads! Thank you sir. I will restore my backup.

ReadingEnjoyer · 02-09-2026, 04:10 PM

I emailed the Calibre Sync developer yesterday. No response yet. The last update was pushed in April 2025. I rely on Calibre Sync and there is no alternative to it.

02-07-2026, 07:01 PM	#1
VelvetElvis Addict Posts: 271 Karma: 20028 Join Date: Jan 2011 Location: Canada Device: Fire HD8, Asus, Sony (T1, PRS-300), Kobo (Glo, Touch, Wireless)	Edited metadata.db. What are the implications? Edited the "books" table in metadata.db as a bandaid fix to the broken Calibre Sync app due to v9 changes. (I added back the "isbn" and lccn" columns) Everything is working fine now, but what are the implications as far as Calibre is concerned? Will this database get rebuilt at some point by something I do? Am I safe to leave these 2 fields back in?

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02-07-2026, 08:21 PM	#2
kovidgoyal creator of calibre Posts: 45,989 Karma: 29579516 Join Date: Oct 2006 Location: Mumbai, India Device: Various	DO NOT mess with metadata.db you risk total data loss if you do. calibre sync has already released a beta simply use that or wait a few more days.

02-07-2026, 08:31 PM	#3
slm (who/what) Posts: 533 Karma: 5065098 Join Date: Feb 2003 Device: Kindle: Voyage,PW1,KOA, Kobo: Clara Colour, Nook GLP, Pocketbook verse	Kovid is of course correct that you should not mess with metadata.db. But his comment that messing up the database can cause complete data loss is saddening. One of the most wonderful features of the early versions of Calibre was that everything could be reconstructed from the book folders themselves. I'm not sure when Calibre lost that level of safety.

02-07-2026, 09:04 PM	#4
kovidgoyal creator of calibre Posts: 45,989 Karma: 29579516 Join Date: Oct 2006 Location: Mumbai, India Device: Various	That works when metadata.db is corrupted and cant be opened, and continues to work to this day. Once you start modifying metadata.db outside of calibre you can do pretty much anything including changing data and those changes will propagate to the distributed backups, leading to the above mentioned total data loss. Simply never modify metadata.db outside of calibre. metadata.db is internal to calibre. And calibre has never been robust against users messing with metadata.db directly and never will be.

02-09-2026, 04:10 PM	#7
ReadingEnjoyer Junior Member Posts: 4 Karma: 10 Join Date: Feb 2026 Device: Phone/Tablet	I emailed the Calibre Sync developer yesterday. No response yet. The last update was pushed in April 2025. I rely on Calibre Sync and there is no alternative to it.

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