Why won't this file open?
Drop it here and find out what it actually is, whether it carries DRM, and exactly what to do about it. Nothing is uploaded — the file is examined inside your own browser.
Why the extension isn't the answer
A filename is a label somebody typed, and it is wrong in
precisely the cases where it matters. A DjVu renamed
.pdf. A folder of scanned pages zipped up and
called .epub. A Kindle book bought from Amazon,
which is byte-for-byte the same kind of container as a free
one right up until you try to read the text.
So this reads the opening bytes instead. Every format leaves
a signature at the very start of the file — %PDF,
PK for anything zip-shaped, a Palm database
header for Kindle books — and that signature cannot be
renamed. Where the name and the contents disagree, this says
so.
The Kindle case is the one worth knowing about. The encryption flag lives in the file header, four kilobytes in, so a DRM-protected book can be identified instantly and with certainty. More on reading books you already own.
Common questions
Is my file uploaded anywhere?
No. The first four kilobytes are read by JavaScript in your own tab, and if you ask for the deeper check the whole file is opened there too. Nothing is transmitted. The simplest proof is to turn off your wifi and try again — it still works, because there is nothing for it to reach.
Why does it say my Kindle book is DRM-protected?
Kindle files carry an encryption flag in their header, and this reads it. If it is set, Amazon has encrypted the text and no browser-based reader can open the file. Books you email to yourself through Send to Kindle are not encrypted and open normally, as do books bought DRM-free from Tor, Baen, Standard Ebooks, Leanpub, No Starch and most academic publishers.
It says my .epub is a zip of images. What does that mean?
An EPUB is a zip archive, and so is a comic book archive or a folder of scanned pages. Some tools produce the second and name it like the first. There is no text inside to read, only pictures of text — running it through OCR produces a file that will open.
Why does the extension not decide the answer?
Because the extension is a name, not a fact, and it is wrong exactly when it matters most. A DjVu renamed to .pdf, a scanned archive named .epub, a DRM-protected Kindle file that looks identical to a free one. This reads the actual bytes at the start of the file, which cannot be renamed.
What can ReadKinetic actually open?
Thirty-nine formats, including EPUB, PDF, Kindle (MOBI, AZW3, PRC), FictionBook, Word, OpenDocument, PowerPoint, LaTeX, Markdown, subtitles and plain text. There is a full list on the formats page, including the ones it refuses and why.
My file is two gigabytes. Will this take a long time?
No. The first check reads only the opening four kilobytes, so its speed does not depend on the size of your file at all. Only the optional deeper check reads the whole thing.
If it does open
ReadKinetic reads it one word at a time, at a pace you set, entirely in your browser — thirty-nine formats, no account, nothing uploaded, and it keeps working with the wifi off. Open the reader →