[Editor Plugin] epubveri

Doitsu · 08-20-2026, 03:27 PM

This very simple plugin allows you to validate the EPUB currently open in the Edit Book tool using epubveri, a pure-Rust EPUB validator.

It automatically downloads/updates the epubveri binary from GitHub as needed and shows validation results in a dock widget, similar to the built-in Check Book tool.

You can select one or more messages using SHIFT/CTRL+click or CTRL+A and copy them to the clipboard as tab-delimited text.
However, this feature might not work in macOS and certain Linux distros.

DISCLAIMER: This plugin was created with the help of Claude.ai.

License: GNU General Public License v3 (GPL-3)

Version History

Spoiler:

JSWolf · 08-20-2026, 03:47 PM

One issue so far. It opens the output window at the bottom of the screen instead of the top where the epubcheck plugin does.

Comfy.n · 08-21-2026, 05:12 AM

Hi!

IMO, the advantage of this implementation is that EPUBCheck and epubveri outputs are displayed in separate UI locations. FYI, I have added epubveri to the calibre Index of Plugins.

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JSWolf · 08-21-2026, 05:57 AM

Quote:

Originally Posted by Comfy.n

Hi!

IMO, the advantage of this implementation is that EPUBCheck and epubveri outputs are displayed in separate UI locations. FYI, I have added epubveri to the calibre Index of Plugins.

Attachment 225294

That's true. What would work is to have an option to have the output window on the bottom or use the one at the top. Because once epubveri is finished, there will be no need for two different windows.

thiago.eec · 08-21-2026, 04:34 PM

Quote:

Originally Posted by Comfy.n

FYI, I have added epubveri to the calibre Index of Plugins.

It can't see it using calibre.

Comfy.n · 08-21-2026, 04:42 PM

Quote:

Originally Posted by thiago.eec

It can't see it using calibre.

Noted, thank you. I'm looking into it. The plugin is there, but there might be an issue with the parser.

JSWolf · 08-21-2026, 04:45 PM

Sometimes it takes a little bit for a new plugin to show up.

JSWolf · 08-23-2026, 11:02 AM

This was updated almost 6 hours ago and the new version is not yet showing up in calibre? Is there something wrong somewhere?

Comfy.n · 08-23-2026, 11:26 AM

Quote:

Originally Posted by JSWolf

This was updated almost 6 hours ago and the new version is not yet showing up in calibre? Is there something wrong somewhere?

Noted. The initial delay for it show up in the plugin updater was likely due to 429 errors on MR side. The current delay for the updater to serve version 0.0.6 could be the same, so let's wait a bit.

JSWolf · 08-23-2026, 11:31 AM

Quote:

Originally Posted by Comfy.n

Noted. The initial delay for it show up in the plugin updater was likely due to 429 errors on MR side. The current delay for the updater to serve version 0.0.6 could be the same, so let's wait a bit.

429 errors? Why so many errors?

Comfy.n · 08-23-2026, 11:32 AM

I mean error type 429

Doitsu · 08-23-2026, 11:38 AM

FYI: I've just checked this. plugins.json.bz2 was updated a couple of minutes ago and the update is now shown in Calibre.

Doitsu · 08-30-2026, 02:58 AM

I've uploaded a new version of the plugin that was modified by @thiago.eec. The new version should improve contrast when dark mode is selected. There's now also a new EPUBCheck style summary at the bottom of the message list.

Kayadelenium · 09-01-2026, 04:46 PM

I read this plugin line by line as well — see the Sigil thread for the long version, since most of what I found applies to both and most of it was our documentation's fault rather than the plugin's.

The short version, all now documented in INTEGRATING.md:

-u decides what the JSON contains. With "show usage messages" off, the summary row at the bottom reports 0 usages — true about the output, false about the book. Pass -u always and let the preference decide what the dock draws.
tool_version is in the envelope, so installed_epubveri_version() need not launch a second process to read epubveri -V.
Prefer musl on Linux over unknown-linux-gnu: static, and runs on distributions where the gnu build will not start.
data.advisory_basis separates NEXT-* (becomes a real error once epubcheck catches up) from ADV-* (never will), if you ever want to show them differently.
Exit code 2 still carries a full report — for a missing file or a directory the JSON on stdout holds the explanation and stderr is empty, so the "epubveri was unable to validate the book" dialog currently shows raw JSON as its detail. Parsing stdout first handles both.
Verifying the download against the release's SHA256SUMS.txt is about twenty lines; the doc has the recipe, and is honest about the modest thing it buys.

One hygiene note. The archive is opened with extractall(), which Python 3.14 changes the default filtering for and which is the classic path-traversal shape. Sigil's plugin extracts a single named member instead, which is the safer pattern of the two.

And credit where it is due, since the Sigil post named places where this plugin is the better of the two: timeouts on every request, draft and prerelease filtering, falling back to the installed binary when GitHub is unreachable, and the clipboard write that verifies and retries. That last one is not obvious knowledge.

Kayadelenium · Yesterday, 12:03 PM

epubveri for calibre 0.1.0, and this is the "I will try to look at it tomorrow" from the Sigil thread.

https://github.com/veripublica/epubv...calibre-v0.1.0

Doitsu — written from calibre's plugin API, with none of your code in it, for the same licensing reason as the Sigil one. Yours is still the one with users, and on Windows and Linux it is the only one: mine has run on macOS and calibre 9.14 and nowhere else. Please leave yours up.

Every finding gets a row with its file, line and message, and activating a row opens the file and puts the cursor on the line. What calibre currently holds is what gets validated, unsaved edits included.

The settings — Preferences / Plugins / epubveri / Customize, and the screenshot is what it looks like. Three switches, all on by default, so out of the box the panel says exactly what the command line says.

Keep epubveri up to date automatically. This one is about your connection rather than about versions. Left on, it reads 842 bytes of checksums at most once an hour and installs a newer epubveri if there is one, verifying it before it runs. Turn it off — a metered link, an air-gapped machine, or preference — and the plugin never touches the network again, and never mentions it. The one thing it still tells you is how old your copy is once a month has passed without a check, because that explains a finding that looks wrong.
Show usage notes. Messages epubcheck also produces but hides unless you pass -u. They are observations, not defects, and they never move the verdict.
Show advisory findings epubcheck does not make. epubveri's own ADV-* checks. Every one of them says so on its own line, and none of them can change VALID or NOT VALID: a book that passes epubcheck passes epubveri.

Two guarantees about those two display switches, because a settings screen is a good place to hide things by accident. Neither can hide an error, a fatal or a warning. And turning one off never makes the report quietly shorter: the summary then says how many findings are not listed and where the switch is.

Two things I could not have found by reading, in case they are worth checking in yours.

container.commit() edits the book. On an EPUB 3 it calls update_modified_timestamp(), so committing the container you are editing — even to a temporary path — rewrites dcterms:modified. Validating would modify the book. Cloning the container first keeps it out.

Cloning alone does not fix it. The timestamp update dirties the OPF, and a dirtied file is re-serialised on the way out rather than copied. calibre's serialiser is not byte-preserving: on my test book it split one line carrying dc:title and dc:language into two and wrote an empty dc:creator as a self-closing tag. The OPF gained a line and every finding below it was reported one line off. Neutralising update_modified_timestamp on the throwaway clone leaves every file byte-identical, which is also what makes the line numbers trustworthy.

Six defects turned up in one day. Five appeared only by running it inside calibre, and the sixth by its own tests, on a fixture whose OPF is laid out the way a person writes one — two real books had missed it. That rate has not flattened, which is why this is 0.1.0 and not 1.0.0.

Bug reports on mine belong on GitHub rather than in your thread. A wrong finding — a wrong error on a good book — is the report I most want, and that one belongs with epubveri itself.

08-30-2026, 02:58 AM	#13
Doitsu Grand Sorcerer Posts: 5,908 Karma: 24240563 Join Date: Dec 2010 Device: Kindle PW2	I've uploaded a new version of the plugin that was modified by @thiago.eec. The new version should improve contrast when dark mode is selected. There's now also a new EPUBCheck style summary at the bottom of the message list. Last edited by Doitsu; 08-30-2026 at 07:49 AM.

09-01-2026, 04:46 PM	#14
Kayadelenium Zealot Posts: 122 Karma: 200000 Join Date: Jul 2026 Location: Planet Earth Device: Kobo Forma	I read this plugin line by line as well — see the Sigil thread for the long version, since most of what I found applies to both and most of it was our documentation's fault rather than the plugin's. The short version, all now documented in INTEGRATING.md: -u decides what the JSON contains. With "show usage messages" off, the summary row at the bottom reports 0 usages — true about the output, false about the book. Pass -u always and let the preference decide what the dock draws. tool_version is in the envelope, so installed_epubveri_version() need not launch a second process to read epubveri -V. Prefer musl on Linux over unknown-linux-gnu: static, and runs on distributions where the gnu build will not start. data.advisory_basis separates NEXT-* (becomes a real error once epubcheck catches up) from ADV-* (never will), if you ever want to show them differently. Exit code 2 still carries a full report — for a missing file or a directory the JSON on stdout holds the explanation and stderr is empty, so the "epubveri was unable to validate the book" dialog currently shows raw JSON as its detail. Parsing stdout first handles both. Verifying the download against the release's SHA256SUMS.txt is about twenty lines; the doc has the recipe, and is honest about the modest thing it buys. One hygiene note. The archive is opened with extractall(), which Python 3.14 changes the default filtering for and which is the classic path-traversal shape. Sigil's plugin extracts a single named member instead, which is the safer pattern of the two. And credit where it is due, since the Sigil post named places where this plugin is the better of the two: timeouts on every request, draft and prerelease filtering, falling back to the installed binary when GitHub is unreachable, and the clipboard write that verifies and retries. That last one is not obvious knowledge.

Yesterday, 12:03 PM	#15
Kayadelenium Zealot Posts: 122 Karma: 200000 Join Date: Jul 2026 Location: Planet Earth Device: Kobo Forma	epubveri for calibre 0.1.0, and this is the "I will try to look at it tomorrow" from the Sigil thread. https://github.com/veripublica/epubv...calibre-v0.1.0 Doitsu — written from calibre's plugin API, with none of your code in it, for the same licensing reason as the Sigil one. Yours is still the one with users, and on Windows and Linux it is the only one: mine has run on macOS and calibre 9.14 and nowhere else. Please leave yours up. Every finding gets a row with its file, line and message, and activating a row opens the file and puts the cursor on the line. What calibre currently holds is what gets validated, unsaved edits included. The settings — Preferences / Plugins / epubveri / Customize, and the screenshot is what it looks like. Three switches, all on by default, so out of the box the panel says exactly what the command line says. Keep epubveri up to date automatically. This one is about your connection rather than about versions. Left on, it reads 842 bytes of checksums at most once an hour and installs a newer epubveri if there is one, verifying it before it runs. Turn it off — a metered link, an air-gapped machine, or preference — and the plugin never touches the network again, and never mentions it. The one thing it still tells you is how old your copy is once a month has passed without a check, because that explains a finding that looks wrong. Show usage notes. Messages epubcheck also produces but hides unless you pass -u. They are observations, not defects, and they never move the verdict. Show advisory findings epubcheck does not make. epubveri's own ADV-* checks. Every one of them says so on its own line, and none of them can change VALID or NOT VALID: a book that passes epubcheck passes epubveri. Two guarantees about those two display switches, because a settings screen is a good place to hide things by accident. Neither can hide an error, a fatal or a warning. And turning one off never makes the report quietly shorter: the summary then says how many findings are not listed and where the switch is. Two things I could not have found by reading, in case they are worth checking in yours. container.commit() edits the book. On an EPUB 3 it calls update_modified_timestamp(), so committing the container you are editing — even to a temporary path — rewrites dcterms:modified. Validating would modify the book. Cloning the container first keeps it out. Cloning alone does not fix it. The timestamp update dirties the OPF, and a dirtied file is re-serialised on the way out rather than copied. calibre's serialiser is not byte-preserving: on my test book it split one line carrying dc:title and dc:language into two and wrote an empty dc:creator as a self-closing tag. The OPF gained a line and every finding below it was reported one line off. Neutralising update_modified_timestamp on the throwaway clone leaves every file byte-identical, which is also what makes the line numbers trustworthy. Six defects turned up in one day. Five appeared only by running it inside calibre, and the sixth by its own tests, on a fixture whose OPF is laid out the way a person writes one — two real books had missed it. That rate has not flattened, which is why this is 0.1.0 and not 1.0.0. Bug reports on mine belong on GitHub rather than in your thread. A wrong finding — a wrong error on a good book — is the report I most want, and that one belongs with epubveri itself. Attached Thumbnails

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08-20-2026, 03:47 PM	#2
JSWolf Resident Curmudgeon Posts: 84,762 Karma: 153788055 Join Date: Nov 2006 Location: Roslindale, Massachusetts Device: Kobo Libra 2, Kobo Aura H2O, PRS-650, PRS-T1, nook STR, PW3	One issue so far. It opens the output window at the bottom of the screen instead of the top where the epubcheck plugin does.

08-21-2026, 05:12 AM	#3
Comfy.n want to learn what I want Posts: 2,426 Karma: 9656783 Join Date: Sep 2020 Device: Libra Colour	Hi! IMO, the advantage of this implementation is that EPUBCheck and epubveri outputs are displayed in separate UI locations. FYI, I have added epubveri to the calibre Index of Plugins.

08-21-2026, 04:45 PM	#7
JSWolf Resident Curmudgeon Posts: 84,762 Karma: 153788055 Join Date: Nov 2006 Location: Roslindale, Massachusetts Device: Kobo Libra 2, Kobo Aura H2O, PRS-650, PRS-T1, nook STR, PW3	Sometimes it takes a little bit for a new plugin to show up.

08-23-2026, 11:02 AM	#8
JSWolf Resident Curmudgeon Posts: 84,762 Karma: 153788055 Join Date: Nov 2006 Location: Roslindale, Massachusetts Device: Kobo Libra 2, Kobo Aura H2O, PRS-650, PRS-T1, nook STR, PW3	This was updated almost 6 hours ago and the new version is not yet showing up in calibre? Is there something wrong somewhere?

08-23-2026, 11:32 AM	#11
Comfy.n want to learn what I want Posts: 2,426 Karma: 9656783 Join Date: Sep 2020 Device: Libra Colour	I mean error type 429

08-23-2026, 11:38 AM	#12
Doitsu Grand Sorcerer Posts: 5,908 Karma: 24240563 Join Date: Dec 2010 Device: Kindle PW2	FYI: I've just checked this. plugins.json.bz2 was updated a couple of minutes ago and the update is now shown in Calibre.