ePub inspector
Drop an ePub file here and see what is inside it.
The file is read in your browser and is never uploaded anywhere. You can close this page and nothing remains.
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What the fields mean
An ePub is a ZIP archive with a fixed shape inside. The version comes from the package document, the contents list comes from the navigation document in ePub 3 or the NCX file in ePub 2, and the document count is the number of XHTML files the book is split into, usually one per chapter. There is more on all of that in the technology of the ePub format.
If the file turns out not to be an ePub at all, that is worth knowing before you try to convert it. A file renamed to .epub is the most common case, and an FB2 book is the second.
The sample above is a real ePub written for this page, and it is free to use for anything. It is a short book about the format it is stored in, so opening it in a reader and inspecting it here show you the same thing from two directions.