Mimetype File Must Be Uncompressed at First Position in ZIP

The mimetype file is either compressed or not the first entry in the ZIP package.

Automated 1-Click Fix Ready

Fix all PKG-009 errors in your EPUB automatically

PreFlight's repackager strictly places the uncompressed mimetype stream at index 0 with compression set to STORE, guaranteeing 100% EPUB 3 spec compliance.

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What This Error Means in Plain English

The EPUB specification requires the file named 'mimetype' containing 'application/epub+zip' to be stored completely uncompressed (STORE method) at byte position 0. Standard zip programs compress everything, which breaks this rule.

Why Retailers & EAA Regulations Block This File

Apple Books, Tolino, and e-readers read the first 68 bytes of the file to determine if it is an EPUB. If compressed or displaced, the file is rejected as corrupted.

Technical Specification: ZIP Local File Header at offset 0 must point to 'mimetype', compression method must be 0 (Stored), and no extra field data should precede it.

Manual Fix Instructions (for Sigil / Calibre)

Do not use normal Windows Right-Click -> 'Send to Compressed Folder' or macOS Finder Archive.
Use terminal command: zip -X0 my-book.epub mimetype && zip -u9r my-book.epub * -x mimetype