An EPUB can pass a format checker and still contain a mistranslated sentence. It can also open in one reader while failing elsewhere because a resource or internal link is broken. A useful check separates those questions instead of treating “the file opened” as a complete result.
Keep the original EPUB and the downloaded translation. Test a working copy so you can compare changes and return to the untouched result if a repair introduces another problem.
Distinguish structure from reading behavior
Structure validation checks whether the publication meets format requirements. Reader testing shows how a particular app displays and navigates it. Language review checks whether the translated meaning is right. None replaces the other two.
For example, a formally valid link may lead to the wrong note. A correct paragraph may render poorly with a missing font. A perfectly displayed sentence may omit a negative. Give each problem an appropriate check rather than expecting one green status to prove the whole book is correct.
The W3C EPUB specification describes the format's content, resources, navigation, and metadata. It is a format reference, not an endorsement of any translator's output.
Start with navigation, resources, and language
Open the EPUB and use its table of contents. Visit early, middle, and final chapters. Compare a heading's destination with the source; a contents list can look complete while its links reach the wrong places.
Check an image, a caption, and a note. Follow the note and return to the body. Confirm that a table is readable and that a long paragraph does not disappear behind a fixed-size container. Change font size and window width to expose problems that a default preview may hide.
Check the edition's title and language information where your tools expose them. Language metadata can affect pronunciation and other reading behavior; bilingual content may require more detailed tagging than a single book-level language. In an EPUB editor, inspect the package OPF’s dc:language: an English-only edition should identify its English content, for example with en; a multilingual publication can declare more than one language. Chapter XHTML has its own lang and xml:lang declarations, which are not inherited from the OPF. In an English–Spanish bilingual chapter, check that an English block is identified as English and its Spanish translation as Spanish—for example, <p lang="es" xml:lang="es">…</p>. These are markup examples to inspect, not a promise of automatic repair. Translating the visible title alone does not update those declarations. Make edits only in a working copy, then validate and retest it.
Use an external EPUB checker for format problems
EPUBCheck evaluates publications against EPUB specifications. Its official site provides installation and getting-started instructions; it is an external tool, not a built-in PDF Craft validation panel.
Follow the current instructions for your environment and run it against the downloaded file. Keep the report with the exact file version. Look at message locations and explanations rather than treating all warnings as interchangeable.
If a report identifies a missing resource or broken reference, inspect that location in a suitable EPUB editor. Work on a copy and avoid bulk changes whose effect you do not understand. Correcting a package issue does not require rewriting translated prose, while a language issue may not appear in the structural report at all.
For a publishing deliverable, follow the destination's current requirements too. A reader's tolerance for a malformed file is not evidence that a store or distributor will accept it.
Test the reader you actually use
Try the same file in your normal reading app and one independent EPUB reader. Focus on the same locations so the comparison tells you something. If one reader alone clips a caption, investigate display behavior; if the image is missing everywhere, inspect the resource or source.
For a Kobo destination, see the Kobo import checks. For an iPad, see translated EPUB reading on iPad. Importing through another service can add a conversion stage, so test the received edition as well as the downloaded EPUB.
| Check | Evidence it gives | Evidence it does not give |
|---|---|---|
| EPUBCheck report | Format conformance problems it detects | Correct translated meaning |
| Two-reader comparison | Whether a display issue is reader-specific | Completeness of every chapter |
| Source comparison | Meaning and structural differences at sampled locations | A guarantee about every unsampled passage |
Recheck after a repair
Save the repaired file under a new version name. Run the structural check again if you changed the package or markup, then revisit the reader locations that originally failed. Also test a nearby chapter and note so you do not solve one link by breaking another.
PDF Craft offers translated or bilingual EPUB downloads, with reading structure retained where possible. It does not promise flawless output or automatic professional validation. After using the EPUB translator, review important passages and structure at a level appropriate to your purpose. Current processing rates are on Pricing.
Keep the source, final EPUB, and any unresolved issues together. That record is more useful than a generic “checked” label when you later change readers or need to revisit a quotation.