Check an EPUB with EPUBCheck, then check the reading
Use the official EPUBCheck project instructions for the current version. Keep the report, investigate errors and follow validation with a source-to-reading comparison.
On this page
Validation checks the file, not the original argument
EPUBCheck examines EPUB file structure and conformance. It cannot know which paragraph belonged in your original PDF or whether a diagram label was cropped away. A successful report is useful for file integrity, but it does not replace source-to-reading inspection. Keep both checks in your workflow.
Use the official release instructions
Obtain EPUBCheck from the official project and follow the instructions for its current release. With an installed Java release bundle, the usual command form is java -jar epubcheck.jar your-book.epub. Use the actual path to your installation and input file. Save the report and version. This is a documented command example; it is not a claim that every article download here has been validated by that command.
Investigate, then read the edition
Locate each reported error in a copy before changing the file. A warning requires interpretation; deleting content simply to silence a message can damage the book. After any repair, rerun the check and inspect the affected passage in a reader. Confirm navigation destinations, paragraphs, images and captions against the PDF. Passing structure and preserving meaning are related but separate requirements.
A concrete example
A structural checker addresses file rules. It does not know which paragraph should have come from your PDF. A file can pass a validator and still leave the reader with incomplete content.
Keep a repair log beside the validation report
For each error you address, record the file version, message and change made. If you rename a resource or alter a contents link, reopen the relevant section afterward. Removing a problematic image merely to obtain a clean report may leave a sentence referring to something no longer present.
Distinguish an untouched raw output from the repaired copy in both filenames and notes. Validation results should refer to the exact copy checked. Then inspect its source-dependent content: a missing paragraph is not necessarily a structural error, and a valid image reference does not establish that the image crop preserved its legend. The combined record makes later checking much easier.
Keep the validator version with the report so another person knows which tool produced the findings. A later version may report different issues. When sharing a repaired edition, identify the exact file checked rather than attaching a report for an earlier copy. Evidence belongs to a version, not only a title.
When a new reading conversion is worth trying
EPUBCheck errors need investigation of the actual EPUB; starting another conversion is not automatically the remedy. If the underlying PDF is awkward to read and you want an adjustable reading edition, EPUBTurn offers a sample for permitted documents. Try that reading task with your PDF, compare the selected passages with the source and validate or inspect the resulting file separately. The sample covers up to 10 automatically selected pages; the current upload limit is 200 MB and full conversion is limited to 100 pages.
Pair structural checks with a real reading task
The actual NASA sample EPUB is a saved output you can validate and read independently. Its retained hardware images and selected text do not erase the generic chapter and list-formatting limitations. Package validity and a usable paragraph answer different questions. EPUBTurn converts a source PDF; it does not repair validation errors in an existing EPUB.
NASA source
D. Harold Shelton, Apollo experience report: Lunar module stabilization and control system, NASA, 1975. US government work; public use permitted. Original pages 3–8 extracted; sample selects excerpt pages 4–6.
Files used in this guide
Download the source files, conversion results or worksheets referenced here. Each label identifies the source document or the converter used.
EPUBTurn actual NASA sample: three selected pages