20 MB EPUB sample
An EPUB file of exactly 20,971,520 bytes. It is a valid EPUB e-book file, generated by this site. Compare its checksum and test it with the parser used by your application. Use it wherever you need a 20 MB sample, test or dummy EPUB file.
Download
sample-epub-20mb.epub
20 MB20,971,520 bytes
Download 20 MB EPUBCreated in your browser in a few seconds, then checked against the SHA-256 checksum. No sign-up.
- Type
- application/epub+zip
- SHA-256
80619f7e43d7e16a9a711aacceb2c700e5bd120a3fc7041d0644643c0b4fd405- Delivery
- Created in your browser from static generator assets (how it works).
What is in this file
A reflowable EPUB 3 book with 12 XHTML chapters, a stylesheet, a navigation document and one test-card PNG that is stored uncompressed and sized so that the book is exactly 20,971,520 bytes. Padding of 11,516,027 bytes in a private ancillary PNG chunk ("spAd", skipped by decoders) inside the image makes up the rest.
| EPUB version | 3.0 |
|---|---|
| Chapters | 12 |
| Embedded image | PNG, 2,048 × 1,536 px |
| Navigation | EPUB 3 nav document |
| DRM | None |
| Container | ZIP (OCF) |
First bytes of the file
The first 64 bytes of sample-epub-20mb.epub as a hex dump: offset, bytes, then the same bytes as text. The EPUB signature is 50 4B 03 04.
00000000 50 4b 03 04 0a 00 00 00 00 00 00 00 21 5c 6f 61 |PK..........!\oa|
00000010 ab 2c 14 00 00 00 14 00 00 00 08 00 00 00 6d 69 |.,............mi|
00000020 6d 65 74 79 70 65 61 70 70 6c 69 63 61 74 69 6f |metypeapplicatio|
00000030 6e 2f 65 70 75 62 2b 7a 69 70 50 4b 03 04 14 00 |n/epub+zipPK....|Preview
EPUB files cannot be shown in a browser. Download the file and open it in an application that reads EPUB, such as Apple Books, Kobo and Google Play Books.
Where 20 MB matters
A 20,971,520-byte file: right at the default attachment limit of Outlook, and just under the 25 MB ceilings of Gmail and GitHub web uploads. These are the default limits a file of this size is useful for testing:
| System | Limit | Note |
|---|---|---|
| Microsoft Outlook | 20 MB of attachments by default for internet mail accounts | This file is right at the limit; add a second attachment and it is exceeded. |
| Gmail | 25 MB per message | Under the limit, although email encoding adds about a third in transit. |
| GitHub web uploads | 25 MiB per file added through the browser | Accepted. Pushing with Git allows larger files. |
| Cloudflare Pages assets | 25 MiB per file | The largest round size that can be served as a static asset. |
| Amazon API Gateway | 10 MB payload | Rejected; the upload has to go directly to object storage. |
| ASP.NET Core (Kestrel) | About 28.6 MB request body by default | Accepted with room for the multipart overhead. |
Use this file for
- Testing image resizing and memory use
- Checking reading-system rendering
- Testing conversion to other formats
Testing notes for EPUB
- Re-zipping an EPUB with a generic tool usually compresses or reorders the mimetype entry, which makes strict readers reject the book.
- EPUB content is HTML, so a reading system that renders it in a web view needs the same script protections as a browser.
Technical details
| File name | sample-epub-20mb.epub |
|---|---|
| Format | EPUB (EPUB e-book) |
| Extension | .epub |
| MIME type | application/epub+zip |
| Size | 20,971,520 bytes (20 MB) |
| Kind | Binary |
| Signature | 50 4B 03 04 |
| SHA-256 | 80619f7e43d7e16a9a711aacceb2c700e5bd120a3fc7041d0644643c0b4fd405 |
| Created | 2026-10-23 |
| Validation | See the listed size and SHA-256. Small downloads are checked in the browser; verify streamed downloads manually. A hash match does not prove parser compatibility. |
| Preview | Not available for this file; details only |
| Source | Generated in your browser by this site's generator; not copied from elsewhere |
| Licence | Free to use, modify and redistribute (terms) |
| Category | Ebooks |
Check the stated structure and checksum against your application requirements. As with any download, scan the file with your own security tools before opening it. How files are made and checked
Verify your copy
This file is created in your browser, so it has no direct URL for curl or wget. The generator is designed to produce reproducible bytes. After saving, compare the checksum with the SHA-256 value above.
sha256sum sample-epub-20mb.epub # Linux
shasum -a 256 sample-epub-20mb.epub # macOSOn Windows, run Get-FileHash sample-epub-20mb.epub -Algorithm SHA256 in PowerShell. For scripts and pipelines, save the file once and keep your own copy.
Related files
Questions about this file
- Is this file exactly 20 MB?
- Yes. It is 20,971,520 bytes, which is 20 MB in the binary units that operating systems and server limits use (1 KB = 1,024 bytes).
- What is inside the 20 MB EPUB file?
- A reflowable EPUB 3 book with 12 XHTML chapters, a stylesheet, a navigation document and one test-card PNG that is stored uncompressed and sized so that the book is exactly 20,971,520 bytes. Padding of 11,516,027 bytes in a private ancillary PNG chunk ("spAd", skipped by decoders) inside the image makes up the rest.
- Do the sample e-books have DRM?
- No. They are unencrypted EPUB 3 files with a navigation document, a stylesheet and one image.