Compress Ebooks to Reduce File Size

Why would I need to compress ebook files?

Ebook compression solves storage and distribution problems. Your EPUB collection takes 5GB but your e-reader only has 4GB total. Your indie book is 25MB with images but distribution platforms have 10MB limits. Your audiobook companion PDF is making downloads slow. Maybe you created an illustrated cookbook at high resolution and need to optimize it for mobile readers, or you're distributing ebooks through email with file size limits.

Different scenarios need different compression levels. Illustrated ebooks can be heavily compressed (60-75% quality) if viewed on screens only. Text-only ebooks need minimal compression since they're already small. Comic books and manga benefit from moderate compression (75-90% quality) to balance detail and file size. Compressing ebooks lets you fit more books on devices, reduce bandwidth costs for distribution, meet platform upload limits, and save storage on cloud libraries.

How does ebook compression work?

Our compressor uses a simple, secure process:

Upload Your Ebook

Drag and drop your ebook file or click to browse. Your file is encrypted during upload using SSL. We support files up to 10MB (covers most ebooks including image-heavy titles).

Choose Compression Settings

Select quality preset (Fast, Normal, Maximum, Ultra) or customize image quality and metadata settings. Our interface shows estimated file size reduction.

Server Processing

Your ebook is compressed on our servers using professional tools. Fast, efficient compression that preserves readability while reducing file size.

Download & Cleanup

Download your compressed ebook. We automatically delete all files from our servers within 1 hour for your privacy. No files are stored permanently.

The entire process typically takes seconds, depending on ebook size and image count. Your original ebook is never modified.

What compression settings should I use?

Choose compression settings based on your needs:

Fast (60% Quality)

Best for quick compression when file size is critical. Reduces images to 60% quality and strips all metadata. Ideal for email attachments, bandwidth-limited distributions, or when storage space is extremely tight.

Normal (75% Quality)

Balanced compression with good quality. Optimizes images to 75% quality while maintaining readability. Best for general use, library optimization, and standard distribution. Most users should start here.

Maximum (90% Quality)

High quality with moderate compression. Preserves 90% image quality and keeps metadata. Ideal for archiving, professional distribution, or illustrated ebooks where visual quality matters.

Ultra (100% Quality)

No quality loss, only removes redundancy. Perfect when you need original quality but slightly reduced file size. Best for master copies, graphic novels, or cookbooks with important photography.

Custom Settings

Use Advanced Options to fine-tune compression. Adjust image quality separately (60/75/90/100%), toggle image optimization, control metadata removal. Perfect for specific requirements like platform upload limits.

Still not sure?

Start with Normal (75%) for most ebooks. Use Fast (60%) for text-heavy novels where images are secondary. Use Maximum (90%) or Ultra (100%) for illustrated books, cookbooks, or graphic-heavy content where visual quality is critical.

Quick guide by content type

Text-only novels: Fast or Normal. Illustrated fiction: Normal or Maximum. Cookbooks/textbooks: Maximum or Ultra. Comic books/graphic novels: Ultra. Technical manuals with diagrams: Maximum.

Remember: You can always re-compress with different settings if the first result isn't ideal. Test the compressed ebook on your device to ensure quality meets your needs.

What's the difference between EPUB, MOBI, and PDF?

Think of EPUB and MOBI as reflowable formats – the text adjusts to fit your screen. You can change font size, and the text reflows like a website. EPUB is the industry standard that works on almost everything except older Kindles. MOBI/AZW3 are Amazon's formats for Kindle devices. They're functionally similar to EPUB but proprietary to Amazon. Modern Kindles now support EPUB via Send to Kindle.

PDF is completely different – it's like a picture of a page. The layout is fixed, fonts and images stay exactly where they are, and you can't adjust text size without zooming (which makes you scroll sideways). PDFs are perfect for textbooks, cookbooks, graphic-heavy content, and anything where layout matters. Terrible for novels on small screens because the text doesn't adapt to your device.

Choosing between them: Use EPUB for novels, fiction, text-based books on any device (Kobo, Nook, iPad). Use PDF for textbooks, manuals, cookbooks, graphic novels, anything layout-dependent. Use MOBI/AZW3 only if you have an old Kindle or are specifically publishing to Amazon (even then, EPUB works fine with Send to Kindle on modern devices).

Can I convert multiple ebooks at once?

Yes! Select multiple ebook files at once (hold Ctrl or Cmd while clicking, or drag multiple files into the upload area). All ebooks will be converted to the same output format you choose. This is perfect for converting your entire ebook library to a different format, preparing books for a new device, or organizing your collection.

After conversion, you can download each ebook individually, or use the 'Download All as ZIP' button to get all converted ebooks in one compressed file. The ZIP option is super convenient when you've converted a book series or collection – instead of downloading 10-20 files individually, you get one organized archive that extracts into all your books properly named.

Keep in mind that ebook conversion is fast for simple formats but can take time for complex books. A typical novel converts in 5-20 seconds. Image-heavy books (cookbooks, graphic novels, textbooks with photos) take longer, maybe 30-60 seconds each. Converting 20 novels might take 3-5 minutes total. For huge batches (100+ books), consider doing them in smaller groups.

How do I convert PDF to EPUB?

PDF to EPUB is tricky because you're converting from fixed-layout (exact positioning) to reflowable (adapting text). It works best with simple, text-heavy PDFs that were created from documents (not scanned). The converter extracts the text, images, and basic formatting, then reflows it into EPUB format. Scanned PDFs (images of book pages) need OCR (text recognition) first, which requires specialized tools.

What works well: Simple PDFs with mostly text, books created from Word/InDesign, technical documents with straightforward layout, and ebooks that were originally digital. What doesn't work well: Scanned books (they're just images), complex multi-column layouts, PDFs with lots of text boxes and fancy positioning, and highly designed books where layout is critical. For best results, start with the original document (Word, InDesign) instead of PDF.

After converting PDF to EPUB, always check the result on your actual device. Text might not flow perfectly, images might move around, and formatting could shift. This is normal – PDF and EPUB are fundamentally different. For professional publishing, use source files (DOCX) rather than PDF. For personal reading, PDF to EPUB works fine for simple books but expect to lose some layout precision.

Can I convert Word documents to EPUB or MOBI?

Yes! This is actually the ideal workflow for authors and self-publishers. Write your book in Word (DOCX), then convert to EPUB/MOBI/PDF for distribution. Word is structured in a way that converts well to ebook formats – much better than starting from PDF or other formats. Most self-published ebooks start as Word documents.

Tips for best results: Use Word's built-in styles (Heading 1 for chapter titles, Normal for body text) instead of manual formatting. Don't use tabs or spaces for indentation – set paragraph indentation in the style. Insert page breaks between chapters (Insert > Page Break). Add a cover image as the first page. Use Word's table of contents feature if you want one. Proper Word formatting converts beautifully to ebooks.

Publishing workflow: Keep your Word document as the master file. When you need to publish, convert it to EPUB for most platforms (Kobo, Apple Books, Google Play). Convert to MOBI or upload EPUB to Amazon KDP for Kindle. If you need to make changes later, edit the Word document and re-convert – don't try to edit the ebook files directly. This keeps everything consistent across formats.

How do I keep formatting during conversion?

Follow these tips to maintain formatting:

Start with source files

Always convert from your original document (DOCX, HTML) rather than PDF or other intermediate formats. Each conversion step loses formatting details. DOCX→EPUB is much better than DOCX→PDF→EPUB.

Use proper document structure

Use Word's built-in styles (Heading 1, Heading 2, Normal) instead of manual formatting (bold, larger font, centered). Styles convert to proper ebook structure. Manual formatting often breaks during conversion.

Keep images reasonable

Include images but don't overdo it. Large images make huge ebook files. Resize images to reasonable dimensions (800-1000 pixels wide is plenty). Use JPEG for photos, PNG for diagrams.

Add metadata before converting

Add title, author, and cover image before conversion. Most converters preserve this information. It helps organize your ebook library and makes books easier to find.

Test on your actual device

After converting, open the ebook on your Kindle, iPad, or whatever device you're using. Different ereaders display formatting slightly differently. Adjust and re-convert if needed.

Summary: Start with well-formatted source files (Word with proper styles), keep images reasonable, add metadata, test on actual devices. Don't expect perfection – ebook formatting is more flexible than print.

Is this really free? What's the catch?

Yes, completely free – no catch, no hidden fees, no premium tiers, no subscriptions. You can convert unlimited ebooks with no watermarks added. We support ourselves through optional donations and non-intrusive ads (which you can block if you prefer). We built this because other ebook converters were either expensive, limited, or filled with annoying upsells.

The only real limitations: File size limit of 10MB per ebook (covers 99% of ebooks including image-heavy titles), and conversion happens on our servers so you need an internet connection. If you need advanced features (fine-tuning table of contents, adjusting cover images, editing metadata), use Calibre desktop software – it's free and more powerful. But for basic ebook conversion, our service works perfectly.

Use your converted ebooks however you want – personal reading, publishing, selling, distribution, whatever (as long as you own the rights or copyright). No attribution required, no restrictions. The ebook files are 100% yours. We delete them from our servers within an hour, so they're truly yours with no strings attached.

What ebook formats do you support?

We support 9 ebook formats:

Main ereader formats (4):

EPUB (universal standard), MOBI (older Kindles), AZW3 (modern Kindles), FB2 (popular in Russia/Eastern Europe)

Legacy formats (5):

LRF (Sony Reader), PDB (Palm devices), RB (RocketBook), SNB (Shanda Bambook), TCR (Psion/Palm compression)

Document formats (4):

PDF (fixed layout), DOCX (Word documents), HTML (web pages), RTF (rich text)

Kindle formats (2):

AZW (Kindle DRM), KFX (Kindle Format 10)

How long does ebook conversion take?

It depends on ebook complexity and file size. As a rough guide: Simple novels (mostly text) convert in 5-15 seconds. Image-heavy books (cookbooks, graphic novels, textbooks) take 20-60 seconds. Complex PDFs with lots of images and formatting take 1-3 minutes. File size matters less than complexity – a 200-page novel converts faster than a 50-page PDF with lots of images and tables.

Format changes matter too. Simple conversions (EPUB to MOBI, both reflowable) are faster than complex ones (PDF to EPUB, converting fixed to reflowable). Batch conversions process files one at a time, so 10 books take about 10x longer than one book. You'll see a progress bar for each file showing estimated time remaining.

If conversion is taking forever: Check your internet connection (slow uploads can stall progress). Make sure your file isn't corrupted (try opening it first). For huge files (10MB+ textbooks with hundreds of images), just be patient – they genuinely take a few minutes. Most everyday ebook conversions finish in under 30 seconds.

Can I use this on my phone or tablet?

Yes! Our converter works on iPhones, iPads, Android phones, and tablets. The interface adapts to touch screens. However, mobile has practical limitations: Uploading large ebook files over cellular data uses a lot of data. Mobile browsers have file size restrictions. Your phone might time out during conversion if the ebook is complex. Most conversions finish quickly, but image-heavy books can take a couple of minutes.

Best practices for mobile: Use WiFi, not cellular data. Convert simpler ebooks (novels work great, complex textbooks might struggle). Keep your screen on during conversion. For serious ebook library management or complex conversions, use a computer. Mobile is perfect for quick single-file conversions like "I just bought this EPUB but need it in MOBI for my Kindle."

If you're having trouble on mobile: Try using your computer instead. Make sure you have a stable WiFi connection. Close other apps to free up memory. Update your browser to the latest version. Some older phones struggle with large file uploads – if it fails repeatedly, the ebook might be too large for mobile conversion.

What happens to my ebook metadata and cover?

Ebook metadata includes title, author, publisher, publication date, description, series info, language, and cover image. This information helps organize your ebook library and makes books easier to find. Our converter attempts to preserve basic metadata when converting between formats that support it (most do). EPUB, MOBI, and AZW3 all support rich metadata including cover images.

What typically gets preserved: Title, author name, publisher, cover image, basic description, and language. What might get lost: Detailed series information, custom tags, ratings, reading progress, and annotations. Different formats support different metadata fields. For example, EPUB has richer metadata support than PDF. Converting from formats with more metadata to formats with less will lose some information.

Best practices for metadata: Add title, author, and cover image to your source document before converting. Use Calibre (free desktop software) for serious metadata management – it's much more powerful than online converters for organizing large ebook libraries. Keep your original files with complete metadata as masters. After conversion, check that essential metadata (title, author, cover) transferred correctly.

Can I convert DRM-protected ebooks?

No, and neither can any legitimate converter. DRM (Digital Rights Management) is copy protection on purchased ebooks from Amazon, Apple, Kobo, and other stores. It's specifically designed to prevent conversion and sharing. Removing DRM is illegal in many countries and violates terms of service. Our converter, like all legal tools, does not remove or bypass DRM protection. This protects authors and publishers from piracy.

What you can do instead: Read DRM-protected books in their native apps (Kindle app for Amazon books, Apple Books for Apple purchases, Kobo app for Kobo books). Buy DRM-free ebooks from stores that don't use DRM (Tor Books, direct from many authors, Smashwords, some publishers). Many publishers now offer DRM-free options when you ask. Use library apps like Libby/OverDrive for borrowing ebooks.

Important note: Only convert ebooks you own the rights to or that are explicitly DRM-free. Public domain books (from Project Gutenberg, for example) are DRM-free and convert perfectly. Your own writing is DRM-free. Purchased DRM-free ebooks are fine to convert. If a book has DRM, you'll need to read it in the platform's app rather than converting it.

What format should I use for self-publishing?

For Amazon Kindle (KDP): Upload EPUB or DOCX directly – Amazon's system converts it automatically to their formats. EPUB works great on modern KDP. If you prefer, you can pre-convert to MOBI or AZW3, but it's not necessary. Amazon handles the conversion and generates formats for different Kindle devices automatically. Make sure your EPUB/DOCX is well-formatted before uploading.

For other platforms (Apple Books, Kobo, Nook, Google Play Books): Use EPUB. It's the universal standard everyone accepts. Draft2Digital and Smashwords also accept EPUB and distribute to multiple platforms. Some platforms accept DOCX and convert it themselves, but EPUB gives you more control over the final result. Use EPUB 2 for maximum compatibility or EPUB 3 if you need advanced features (multimedia, interactivity).

Professional workflow: Write your book in Word (DOCX) using proper styles and formatting. Convert to EPUB for distribution. Upload EPUB to Amazon KDP (they convert it), Apple Books, Kobo, Nook, etc. Keep your DOCX as the master file – when you need to make changes, edit the Word document and re-convert to EPUB rather than trying to edit the EPUB directly. Test your EPUB on actual devices (Kindle, iPad, Android) before publishing to make sure formatting looks good.