What happens to your file after you upload it
You press upload, a progress bar fills, and then nothing visible happens for a while. Most of the confusion authors have with stores lives in that gap: the rejection that makes no sense, the preview that does not match your file, the correction that takes days to appear.
None of it is mysterious once you know what is going on in there. No store publishes its pipeline, the details differ between them, and they change — so read the stages below as a map of the territory, not a timetable.
The stages, in rough order
The file is checked automatically. Software examines the EPUB against the specification: is every file it references actually packaged, does the navigation match the real chapters, are the required metadata fields present and well formed. This runs first, because everything downstream assumes a sound file.
It is converted. The store builds its own delivery format from your EPUB — the version its apps and devices will render. Your file is the input, not the thing readers receive.
Metadata is compared. The title, author and language stored inside your file are read out and set against the fields you typed into the upload form. Two sources of truth now exist for the same facts.
The cover is extracted. Pulled from the file or from your separate upload, then resized into the several thumbnails the store needs — search results, category lists, a phone.
A preview is built. The store generates the sample readers will see, usually from the converted file rather than from yours.
The listing is queued for review. Some mixture of automated checks and human attention, on a timetable that varies by store, by season, and by whether anything about your submission drew a second look.
What that explains
Why a file that opens fine can still be rejected. Reading apps are built to show the reader something rather than an error. They patch broken markup, skip a missing image, guess at structure that was never declared. The checker has the opposite job. Opening your file proves it is not catastrophically broken; it proves nothing else. What makes an EPUB pass validation covers what the checker looks at.
Why the store's preview does not look like your file. It is a different rendering of a converted file, on a different engine, with the store's own defaults for type size and margins on top. Differences in line breaks, spacing and where a chapter lands on screen are expected. Differences in structure — a chapter that has stopped being a chapter, an image that is gone — are not, and those point back at the conversion, which points back at your file.
Why metadata mismatches matter more than they seem to. Nobody is offended that your file says "J.A. Smith" and your form says "J. A. Smith". The store has two sources for one fact and they disagree, and disagreement suggests the file was made for something else — a different edition, an earlier title, another pen name.
Why a re-upload takes time to appear. Your correction goes through the whole sequence again, not just the part you changed, and the new build has to reach a distribution network that caches things. See Updating an ebook after it is published.
In the Interior Formatter. The EPUB 3 it builds validates with zero errors and zero warnings under epubcheck and carries the title, author and language straight from your book's own fields — which clears the first two stages above before you ever open an upload form. Start your ebook → · about the Interior Formatter
The one thing to do before uploading at all
Validate the file. That is it.
The automated structural check is the first gate and the largest single category of rejection, and it is the only stage that gives a definite answer — the file either conforms or it does not, and the report names the line. Every other stage involves judgment, comparison or timing. This one does not, and you can run it yourself in advance.
Check these four things at the visible points
You cannot watch the pipeline, but it surfaces four times before your book goes live.
The preview, after conversion. Read the opening pages and jump through the chapter navigation. You are not proofreading here — do that in your own file — you are checking that the structure survived: chapters where chapters should be, images present, no run of text collapsed into one block.
The thumbnail, at the size it will really appear. Shrink the browser or step back from the screen. A cover that works at full size can lose its title entirely at list size, and this is the only place you see the store's own resizing of it. Ebook cover size, and why it is not your print front covers building for that.
Where the sample starts and stops. The extract is generated, and it often begins in your front matter, so a reader's free look can be a title page, a copyright page and a dedication. The sample, and what it is selling explains what to do about it.
The listing fields, read as a stranger. Title, subtitle, series and number, author spelling, language, description. Compare them character by character against what is inside your file, then read the page itself the way a browsing reader would — Check the listing the way a stranger would.
When it comes back rejected
Read the message as a pointer to a stage rather than as a diagnosis. Those notices are assembled from a short list of standard reasons, so they name a category, not your specific problem. When a store rejects your ebook works through the categories and the order to attack them in.
And expect none of this to sit still. Review times, checks and the rules behind them differ between stores and change without notice, so the store's own current help page is the only authority on how long anything takes.
Make your ebook
The tools are free to use: bring your manuscript once and get both a print PDF and an EPUB out of the same source, so the two editions cannot drift apart. You only pay when you want the files without the preview watermark.
Next: When a store rejects your ebook · More: Ebook file formats, plainly · Uploading your files for the first time · Checking an ebook before you publish it