How to Preview Your Ebook on Different Devices Before Publishing

You can preview your ebook on different devices before publishing by using free desktop tools like Kindle Previewer and Calibre, retailer-specific online previewers built into KDP and Draft2Digital, and by side-loading your EPUB or MOBI file onto physical e-readers, tablets, and phones. Testing across multiple screens is the single most reliable way to catch formatting problems before readers do.

Why Previewing on Multiple Devices Matters

An ebook that looks perfect on your laptop screen may break on a Kindle Paperwhite, reflow awkwardly on a phone, or lose its formatting entirely on a Kobo. This happens because reflowable EPUBs render differently depending on the reading app, screen size, and the CSS support each platform provides. A heading that centers beautifully in Apple Books might left-align on an older Kindle; an image that fills the screen on a tablet might overflow on a phone.

The core issue is that you are not publishing a fixed document. Unlike a print PDF where every reader sees the same page, a reflowable ebook adapts to each device. The reader controls font size, line spacing, and sometimes margins. Your job is to make sure the book holds together across all of those variations.

Previewing also catches conversion artifacts that are invisible in your source file. If you formatted your manuscript in Word and converted to EPUB, elements like embedded fonts may not carry over, tab-based indentation may collapse, and page-level vertical centering (common on title pages) will be ignored by the reflowable engine.

What Desktop Preview Tools Are Available?

Several free desktop applications let you open and inspect your ebook file before uploading it to any retailer. Each has different strengths.

Kindle Previewer 3

Amazon’s Kindle Previewer 3 is a free desktop application for Mac and Windows that simulates how your book will look on Kindle devices and apps. It accepts EPUB, MOBI, KPF, and DOCX files. When you open a file, Kindle Previewer converts it to Amazon’s internal KPF format using the same engine KDP uses during publishing, so what you see in the previewer is very close to what Kindle customers will see.

Kindle Previewer lets you switch between simulated devices: Kindle E-reader (the e-ink Paperwhite view), Kindle Fire tablet, iPhone, and iPad. You can toggle between portrait and landscape orientation and adjust font size. It also includes an Enhanced Typesetting indicator that shows whether your book qualifies for Amazon’s improved rendering features. If your book is destined for KDP, this tool is essential.

Calibre

Calibre is a free, open-source ebook management application available on Mac, Windows, and Linux. Its built-in ebook viewer supports EPUB 2, EPUB 3, MOBI, AZW3, and several other formats. Calibre’s viewer renders EPUBs using its own engine, which means it does not perfectly replicate any single retailer’s reading app. However, it is excellent for spotting structural problems: broken tables of contents, missing chapter breaks, images that don’t display, and CSS that fails silently.

Calibre also includes an “Edit Book” feature that lets you inspect the underlying HTML and CSS inside your EPUB. If something looks wrong in the viewer, you can open the editor to diagnose exactly which element is misbehaving.

Apple Books (Mac)

If you have a Mac, you can open any EPUB file directly in Apple Books by double-clicking it. This gives you a pixel-accurate preview of how the book will appear to Apple Books customers. Apple Books has strong EPUB 3 support, including embedded fonts, media overlays, and advanced CSS. If you distribute through Apple Books via Draft2Digital or direct upload, previewing here is important because Apple’s rendering engine differs from Kindle’s in how it handles margins, font fallbacks, and image scaling.

Thorium Reader

Thorium Reader is a free, open-source EPUB reader for Windows, Mac, and Linux developed by the EDRLab foundation. It supports EPUB 2 and EPUB 3, including fixed-layout EPUBs. Thorium is useful for testing because it closely follows the EPUB specification, making it a good baseline check for standards compliance.

How Do Retailer Online Previewers Work?

Most ebook retailers provide an online preview tool during the upload process. These previewers run the same (or very similar) conversion and rendering pipeline that the retailer uses for the final published version, making them the most authoritative preview for that specific platform.

Amazon KDP: After uploading your manuscript file during the publishing workflow, KDP offers an online previewer that lets you flip through the converted book. This previewer simulates both tablet and e-reader views. It also flags conversion warnings (like images below 300 DPI or unsupported fonts). The KDP online previewer uses the same conversion engine as Kindle Previewer 3, so if you have already tested locally, the results should match.

Draft2Digital: D2D converts your uploaded file to EPUB and provides a downloadable preview file. You can open this EPUB in any reader application to see how D2D’s conversion handled your formatting. Because D2D distributes to Apple Books, Kobo, Barnes & Noble, and other retailers, testing the D2D-generated EPUB is a good way to catch issues that will affect multiple storefronts simultaneously.

Kobo Writing Life: Kobo’s self-publishing platform accepts EPUBs directly and provides a preview within the dashboard. Since Kobo e-readers have their own rendering engine (distinct from both Kindle and Apple Books), this preview is the best way to check Kobo-specific behavior.

If you have already validated your EPUB with EPUBCheck before uploading, most retailer previews will proceed without conversion errors. Validation catches structural problems; retailer previews catch rendering differences.

How to Side-Load Your Ebook onto Physical Devices

Desktop previewers and retailer tools simulate device behavior, but nothing replaces testing on an actual device. Side-loading means transferring your ebook file directly to a physical e-reader, tablet, or phone so you can see exactly what a reader will see.

Kindle devices

Amazon’s Send to Kindle service lets you email an EPUB or MOBI file to your Kindle’s unique email address (found in your Amazon account under “Manage Your Content and Devices”). The file is converted and delivered to your Kindle within minutes. This is the most accurate test for Kindle customers because it goes through Amazon’s full conversion pipeline. You can also use the Send to Kindle desktop app or connect your Kindle via USB and copy files to the “documents” folder.

Kobo devices

Connect your Kobo e-reader to your computer via USB. The device appears as an external drive. Copy your EPUB file into the root directory or any subfolder. Disconnect the device, and the book will appear in your library after the Kobo indexes it. This gives you a direct view of how Kobo’s e-ink rendering handles your formatting, fonts, and images.

Phones and tablets

Install the Kindle app, Apple Books, or a third-party EPUB reader (like Aldiko or PocketBook) on your phone or tablet. Transfer the file via email, cloud storage, or direct download. Phone screens are the most constrained reading environment; if your formatting holds on a 6-inch phone display, it will generally work everywhere else.

What Should You Check During an Ebook Preview?

A thorough ebook preview is not just flipping through the pages. Focus on these specific areas where formatting problems most commonly appear.

Table of contents: Open the TOC and tap every entry. Each link should jump to the correct chapter. Check both the HTML table of contents (the page inside the book) and the NCX/navigation table of contents (the one the reading app generates in its menu). These are separate structures and can break independently.

Title page and front matter: Centering, spacing, and image placement on title pages are the most common casualties of reflowable conversion. If your title page was designed with precise vertical positioning in Word, it will almost certainly not survive conversion to EPUB as a reflowable element.

Images: Check that every image displays, scales proportionally, and is sharp enough to read on the device. On e-ink screens, verify that images with fine detail or small text are still legible. Check images at both the default and enlarged font sizes, since increasing font size can cause images to reflow or scale differently.

Chapter breaks: Every chapter should start on a new screen. If two chapters run together on the same page, your page breaks did not convert correctly.

Special characters and formatting: Look for missing em dashes, curly quotes that reverted to straight quotes, accented characters that display as question marks, and bold or italic styling that disappeared. Check any bulleted or numbered lists, block quotes, and centered text.

Font size extremes: Increase the font size to the maximum setting and decrease it to the minimum. Your layout should remain readable at both extremes. Large font sizes reveal margin and spacing problems; small sizes reveal elements that depend on specific line breaks to look right.

A Practical Preview Workflow Before You Hit Publish

A structured preview workflow saves time and ensures consistent coverage. Here is a practical sequence that balances thoroughness with efficiency.

Step 1: Validate first. Run your EPUB through EPUBCheck before any visual preview. Fix all errors and warnings. There is no point previewing a file that has structural problems; you will be previewing the same file again after fixing them.

Step 2: Desktop preview. Open the file in Kindle Previewer (if publishing to KDP) and one general-purpose EPUB reader like Calibre or Thorium. Flip through the entire book in each tool. Check the TOC, images, front matter, and chapter breaks.

Step 3: Retailer preview. Upload to your target platforms and use their built-in previewers. If the retailer flags warnings, address them before continuing.

Step 4: Physical device test. Side-load onto at least one physical device, ideally an e-ink reader and a phone. These two form factors cover the most common rendering edge cases. Read at least the first three chapters, the last chapter, and any pages with images or special formatting.

Step 5: Fix and re-test. If you find issues, fix them in your source file (not the EPUB directly), re-export, and repeat from Step 1. Editing the EPUB directly can introduce new problems, and you will lose those changes the next time you export from your source.

Frequently Asked Questions

Do I need to preview on every device and app available?

No. Testing on every possible combination is impractical. Focus on the platforms where you will actually distribute. At minimum, test in Kindle Previewer (for Amazon) and one general EPUB reader (for everything else). Adding a physical e-reader and a phone covers the most common edge cases.

Is Kindle Previewer the same as the KDP online previewer?

They use the same underlying conversion engine, so the results should be very similar. Kindle Previewer 3 runs locally on your desktop and lets you test before uploading. The KDP online previewer runs after you upload your file during the publishing process. Either one gives you an accurate representation of how the book will look on Kindle devices.

Can I preview a Word file directly or do I need to convert to EPUB first?

Kindle Previewer accepts Word (DOCX) files directly and converts them using Amazon’s engine. For other platforms, you will need an EPUB. If you upload a Word file to Draft2Digital, they convert it to EPUB for you and provide the converted file for preview. Generally, converting to EPUB yourself gives you more control over the output.

What if my ebook looks different on every device I test?

Minor differences between devices are normal and expected. Font rendering, margin sizes, and line spacing will vary because each reading app interprets the EPUB specification slightly differently. The goal is not pixel-perfect consistency; it is ensuring that no device produces broken formatting, missing content, or unreadable text.

Does EPUBCheck replace visual previewing?

No. EPUBCheck validates the technical structure of your EPUB file against the EPUB specification. It catches errors like malformed HTML, missing required files, and invalid metadata. But a file can pass EPUBCheck with zero errors and still look terrible on a Kindle because of poor CSS, oversized images, or formatting choices that are technically valid but visually broken. You need both validation and visual preview.