Calibre v9 DB changes break calibre-web

dinosm · 01-30-2026, 10:02 AM

Calibre v9 has made changes to its DB schema resulting in a broken calibre-web.

Calibre-web shows me an empty library, and when I click on e.g. 'About', it gives an error message about DB errors which include the fact that book.isbn is missing from the DB.

DB changes were not documented in the website changelog, it would have been helpful to have those mentioned there.

Now, I am guessing the only robust way to fix this is to wait for calibre-web's developer to update their software, but I'm just posting this here as I updated Calibre today and couldn't find anything online about this issue.

I ended up downgrading Calibre back to 8.x, and restoring a backup of its database to get my calibre-web back.

kovidgoyal · 01-30-2026, 10:43 AM

calibre's database schema is not a stable API. The only stable way to access the calibre database is via the calibre python APIs or the calibre server JSON APIs. Changes to the database schema are internal changes. Internal changes are not documented in the changelog. And just for the record three unused columns from the books table have been deleted. These columns were *never* used for anything and were just cluttering the schema. I have no idea what calibre web was using those columns for but yes, it needs to be changed.

dinosm · 01-30-2026, 10:53 AM

Thank you so much for replying and explaining this Kovid!
I guess calibre-web accesses the database directly rather than use an API.
I'll post on their github to hopefully get some traction their end.

Thank you for all the work you put in!

JSWolf · 01-30-2026, 11:35 AM

Quote:

Originally Posted by dinosm

Thank you so much for replying and explaining this Kovid!
I guess calibre-web accesses the database directly rather than use an API.
I'll post on their github to hopefully get some traction their end.

Thank you for all the work you put in!

The calibre-web developer could have come to Mobileread and been part of the beta and have a version of calibre-web available on launch day. Plus, calibre-web is doing something they should not have been doing since it's now broken.

If you do find out what calibre-web was doing that caused it to break, please post here. And I hope calibre-web is not doing any writing of anything to the database.

slm · 01-30-2026, 12:21 PM

I don't know Calibre-Web at all, but it is worth noting that the "correct" solution of using the Caliber API is not available in many real-life use cases.

Programs that use the Calibre data, such as Calibre Sync (and probably Calibre Web) typically do not access the actual machine Calibre is running on, but instead access the library on drobox or similar cloud storage. So they can only access the database file directly if they want the database info.

They could a different strategy when accessing dropbox--one can build a simplified database from the directory structure information available in dropbox and use it to access the book thumbnails and covers and the actual books. (I do this because I don't like playing with db files.) I don't think this is workable for general use because tracing the directory structure is rather time-comsuming.

kovidgoyal · 01-30-2026, 09:15 PM

Regardless, that does not mean the calibre database schema suddenly becomes stable API just because some programs choose to use it that way. Look at the file schema_upgrades.py in the calibre source code. You will see the schema has been changed over twenty times in the past decade+

slm · 01-30-2026, 10:10 PM

@kovidgoyal:
Apologies.

I wasn't suggesting that you shouldn't make changes as you wish, particularly since Calibre warns against using various cloud services for the library.

I was trying to explain why the APIs don't work for some "hacks".
As I mentioned, for many purposes, analyzing the directory structure on the cloud-based memory is possible and doesn't suffer from the problems of a varying database structure.

I've always thought that one of Calibre's best features is that the basic library can be "reconstructed" from the file structure--in the distant past I've actually had to use that feature!

Again, thank you for creating and maintaining Calibre.

Dirk-71 · 02-01-2026, 12:11 PM

I found a quick fix....here...

https://davidroessli.com/logs/2026/0...re-web-server/

This works in my case (Calibre-Web on Synology NAS DS 220+ - Container Manager). I synchronize my Calibre Database from my HardDisk to my NAS. Any time I synchronize it, I have to run the script using ssh to get the issue fixed.

It's a temporary solution until Calibre-Web gets updated accordingly.

JSWolf · 02-01-2026, 03:23 PM

Quote:

Originally Posted by Dirk-71

I found a quick fix....here...

https://davidroessli.com/logs/2026/0...re-web-server/

This works in my case (Calibre-Web on Synology NAS DS 220+ - Container Manager). I synchronize my Calibre Database from my HardDisk to my NAS. Any time I synchronize it, I have to run the script using ssh to get the issue fixed.

It's a temporary solution until Calibre-Web gets updated accordingly.

See post #10 of this thread. calibre-web is not going to be updated. You'll have to use caibre-web automated.

https://www.mobileread.com/forums/sh...d.php?t=371848

Dirk-71 · 02-01-2026, 03:36 PM

Quote:

Originally Posted by JSWolf

You'll have to use caibre-web automated.

Dirk-71 · 02-06-2026, 07:36 AM

Calibre-Web Automated is not an option for me. I don't like the dark look (cannot be changed anymore in the latest version) and the performance is weak in comparison to the original CW. I will keep on using the script to keep the original CW running.

rantanplan · 02-06-2026, 10:34 AM

Quote:

Originally Posted by Dirk-71

Calibre-Web Automated is not an option for me. I don't like the dark look (cannot be changed anymore in the latest version) and the performance is weak in comparison to the original CW. I will keep on using the script to keep the original CW running.

Use the nightly build of Calibre-web and you're also good.

JSWolf · 02-06-2026, 10:44 AM

Quote:

Originally Posted by rantanplan

Use the nightly build of Calibre-web and you're also good.

Are you saying that the nightly build is compatible with calibre 9.2?

rantanplan · 02-06-2026, 12:16 PM

Quote:

Originally Posted by JSWolf

Are you saying that the nightly build is compatible with calibre 9.2?

https://github.com/janeczku/calibre-...ent-3828194314

Dirk-71 · 02-06-2026, 04:28 PM

How can I set in "Container Manager" that I get the nigthlies instead of the latest versions? That's not clear for me.

UPDATE....found it my self....!

I can confirm that the latest nightly 5a1f3d8e is working fine with Calibre 9.x.

02-06-2026, 04:28 PM	#15
Dirk-71 Groupie Posts: 186 Karma: 46112 Join Date: Dec 2016 Location: Germany Device: Kobo: Clara BW, Libra 2, Aura One, Aura H2O	How can I set in "Container Manager" that I get the nigthlies instead of the latest versions? That's not clear for me. UPDATE....found it my self....! I can confirm that the latest nightly 5a1f3d8e is working fine with Calibre 9.x. Last edited by Dirk-71; 02-06-2026 at 04:46 PM. Reason: Solved!

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01-30-2026, 10:02 AM	#1
dinosm Member Posts: 22 Karma: 198 Join Date: Nov 2024 Device: Pocketbook Inkpad Color 3	Calibre v9 DB changes break calibre-web Calibre v9 has made changes to its DB schema resulting in a broken calibre-web. Calibre-web shows me an empty library, and when I click on e.g. 'About', it gives an error message about DB errors which include the fact that book.isbn is missing from the DB. DB changes were not documented in the website changelog, it would have been helpful to have those mentioned there. Now, I am guessing the only robust way to fix this is to wait for calibre-web's developer to update their software, but I'm just posting this here as I updated Calibre today and couldn't find anything online about this issue. I ended up downgrading Calibre back to 8.x, and restoring a backup of its database to get my calibre-web back.

01-30-2026, 10:43 AM	#2
kovidgoyal creator of calibre Posts: 46,062 Karma: 29579868 Join Date: Oct 2006 Location: Mumbai, India Device: Various	calibre's database schema is not a stable API. The only stable way to access the calibre database is via the calibre python APIs or the calibre server JSON APIs. Changes to the database schema are internal changes. Internal changes are not documented in the changelog. And just for the record three unused columns from the books table have been deleted. These columns were never used for anything and were just cluttering the schema. I have no idea what calibre web was using those columns for but yes, it needs to be changed.

01-30-2026, 10:53 AM	#3
dinosm Member Posts: 22 Karma: 198 Join Date: Nov 2024 Device: Pocketbook Inkpad Color 3	Thank you so much for replying and explaining this Kovid! I guess calibre-web accesses the database directly rather than use an API. I'll post on their github to hopefully get some traction their end. Thank you for all the work you put in!

01-30-2026, 12:21 PM	#5
slm (who/what) Posts: 552 Karma: 5338704 Join Date: Feb 2003 Device: Kindle: Voyage,PW1,KOA, Kobo: Clara Colour, Nook GLP, Pocketbook verse	I don't know Calibre-Web at all, but it is worth noting that the "correct" solution of using the Caliber API is not available in many real-life use cases. Programs that use the Calibre data, such as Calibre Sync (and probably Calibre Web) typically do not access the actual machine Calibre is running on, but instead access the library on drobox or similar cloud storage. So they can only access the database file directly if they want the database info. They could a different strategy when accessing dropbox--one can build a simplified database from the directory structure information available in dropbox and use it to access the book thumbnails and covers and the actual books. (I do this because I don't like playing with db files.) I don't think this is workable for general use because tracing the directory structure is rather time-comsuming.

01-30-2026, 09:15 PM	#6
kovidgoyal creator of calibre Posts: 46,062 Karma: 29579868 Join Date: Oct 2006 Location: Mumbai, India Device: Various	Regardless, that does not mean the calibre database schema suddenly becomes stable API just because some programs choose to use it that way. Look at the file schema_upgrades.py in the calibre source code. You will see the schema has been changed over twenty times in the past decade+

01-30-2026, 10:10 PM	#7
slm (who/what) Posts: 552 Karma: 5338704 Join Date: Feb 2003 Device: Kindle: Voyage,PW1,KOA, Kobo: Clara Colour, Nook GLP, Pocketbook verse	@kovidgoyal: Apologies. I wasn't suggesting that you shouldn't make changes as you wish, particularly since Calibre warns against using various cloud services for the library. I was trying to explain why the APIs don't work for some "hacks". As I mentioned, for many purposes, analyzing the directory structure on the cloud-based memory is possible and doesn't suffer from the problems of a varying database structure. I've always thought that one of Calibre's best features is that the basic library can be "reconstructed" from the file structure--in the distant past I've actually had to use that feature! Again, thank you for creating and maintaining Calibre.

02-01-2026, 12:11 PM	#8
Dirk-71 Groupie Posts: 186 Karma: 46112 Join Date: Dec 2016 Location: Germany Device: Kobo: Clara BW, Libra 2, Aura One, Aura H2O	I found a quick fix....here... https://davidroessli.com/logs/2026/0...re-web-server/ This works in my case (Calibre-Web on Synology NAS DS 220+ - Container Manager). I synchronize my Calibre Database from my HardDisk to my NAS. Any time I synchronize it, I have to run the script using ssh to get the issue fixed. It's a temporary solution until Calibre-Web gets updated accordingly.

02-06-2026, 07:36 AM	#11
Dirk-71 Groupie Posts: 186 Karma: 46112 Join Date: Dec 2016 Location: Germany Device: Kobo: Clara BW, Libra 2, Aura One, Aura H2O	Calibre-Web Automated is not an option for me. I don't like the dark look (cannot be changed anymore in the latest version) and the performance is weak in comparison to the original CW. I will keep on using the script to keep the original CW running.