Changing a Japanese EPUB into an English edition is not a one-field edit from ja to en. The body, chapter labels, dc:language, and output artifact need to move together as a new edition. In this test, matched two-chapter Japanese and English editions were exported from separate workspaces and checked for OPF language, navigation labels, filenames, and local structural validity.
Answer: Rebuild the publication as a separate language edition
A reliable conversion workflow preserves the Japanese source, creates an English workspace, replaces the body and chapter labels, changes the publication language to en, and exports to a new filename. Editing only the OPF inside an existing EPUB can leave Japanese navigation or body content behind and makes the authoritative edition unclear.
Use four surfaces as the preflight:
- Body: Does the manuscript use the target language?
- Package: Does
dc:languageidentify that language? - Navigation: Do the chapter labels match the edition?
- Artifact: Is the new edition stored separately from the original?
STUDIO-416 covers the initial language setting for a new book. This article covers the change from an existing Japanese edition to a separately preserved English edition.
Sample: A before-and-after table for two chapters
The sample paired a two-chapter Japanese edition with a two-chapter English edition built from the same structure.
| Surface | Before | After |
|---|---|---|
| Body and chapter labels | Japanese | English |
| Source-card language | ja |
en |
| Workspace | Japanese edition | English edition |
| Output | studio-418-260831.120000.epub |
english-edition-studio-418-260831.120000.epub |
Fixing these starting values makes two common mistakes visible: importing the English manuscript while leaving ja on the source card, or exporting the English edition over the Japanese file.
Procedure: Preserve, duplicate, replace, export, and read back
The edition-change sequence was:
- Preserve the Japanese workspace and EPUB as the before-state.
- Create a separate English workspace and add the English body and chapter labels.
- Change the source-card language to
en. - Export the English edition under a different name.
- Read
dc:languagefrom both OPF files. - Inspect both navigation documents for language-appropriate chapter labels.
- Run local structural validation on both outputs.
The article-specific Stage 4 run used 20 commands. A wrong OPF value returns to the source-card setting. Wrong navigation text returns to the chapter labels. A filename collision returns to the export destination. A body-language mismatch returns to the manuscript rather than being concealed by metadata.
Measured result: Both editions remained distinct and internally aligned
The article-specific status was passed. The Japanese OPF reported ja, the English OPF reported en, the output names were separate, each navigation document used the expected language, and both files returned valid: true.
| Read-back check | Japanese edition | English edition |
|---|---|---|
dc:language |
ja |
en |
| Navigation labels | Japanese confirmed | English confirmed |
| Local validation | valid: true |
valid: true |
This was not a round-trip toggle inside one file. The two editions remained in separate workspaces and separate artifacts, and each artifact was inspected independently.
A different common regression sample used four chapters, horizontal writing, and version 1.8. Its nine-command export produced spine count 8, one image, no missing resources, nav and NCX documents, and valid: true. That measurement checks the general export path and is separate from the two-chapter language-change sample.
Limits: Colophon strings and external presentation need another check
Rune Studio documents language-dependent navigation, colophon, and date formatting. The article-specific result values, however, explicitly confirm the OPF languages, navigation languages, separate outputs, and local validation. Although the run inspected colophon files, its summarized result values do not list the exact compared strings. A release preflight should therefore open the colophon and visually verify its language and date format.
Retailer language fields, retailer review, and presentation in external reading systems were not tested. valid: true is a local structural result; it is not a claim of universal retailer acceptance or identical device rendering.
What Rune Studio covers
Rune Studio’s documented EPUB wizard lets a user set publication language, chapter order and navigation, version, and publication date before generating EPUB 3. Japanese- and English-specific navigation, colophon, and date formatting are documented Stage 3 features.
The two exported editions, their ja and en OPF values, language-matched navigation, separate filenames, and two successful local validations are Stage 4 observations. General package requirements are available in W3C EPUB 3.3, while the documented product scope is summarized on the Rune Studio website.
Conclusion: Keep the before-state and verify the new edition against it
A Japanese-to-English EPUB change should preserve the Japanese edition and rebuild the English edition as a complete artifact: English body, English chapter labels, en, and a distinct filename. The two-chapter test confirmed that the OPF, navigation, output name, and local validity remained aligned for both editions.
If a preflight item fails, return to the setting that owns it. The source card owns publication language, the manuscript owns body and chapter labels, the export settings own the filename, and the final visual review owns the colophon. Retailer and external-device checks remain separate.
