Convert EPUB to AZW3 Online — For Best Kindle Typography
Custom fonts, advanced layouts, and CSS3 styling on modern Kindles.
Drop up to 50 EPUBs at once — no install, no sign-up required.
Drop EPUB Files Here
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How it works
- 1 · Drop your files
Drag & drop or choose EPUB files. No account required—paid plans unlock bigger batches, higher limits, and priority queues.
- 2 · We convert securely
Processed on our dedicated servers using Calibre. Encrypted in transit & at rest. We never store filenames—only file types & sizes for accounting.
- 3 · Download & auto-delete
Grab your AZW3 files in seconds. Files delete automatically after 1 hour. Delete anytime after downloading with one click.
EPUB (Electronic Publication) is an open ebook standard developed by the International Digital Publishing Forum (IDPF), now part of the W3C. First released in 2007 as a successor to Open eBook, EPUB has become the most widely supported ebook format. EPUB files are ZIP archives containing HTML/XHTML content, CSS styling, images, and metadata organized according to the EPUB specification.
Learn more: EPUB on Wikipedia
EPUB's key feature is reflowable content—text automatically adapts to different screen sizes, making it ideal for e-readers, tablets, and phones. The format supports embedded fonts, multimedia (in EPUB 3), and accessibility features. Most e-readers except Amazon Kindle natively support EPUB.
AZW3, also known as KF8 (Kindle Format 8), is Amazon's modern ebook format introduced in 2011 with the Kindle Fire. AZW3 files use the .azw3 extension and support HTML5, CSS3, and advanced typography features not available in the older MOBI format.
Learn more: KF8/AZW3 on MobileRead Wiki
AZW3 offers superior formatting capabilities compared to MOBI, including custom fonts, embedded audio/video, SVG graphics, and complex layouts. It's the recommended format for modern Kindle devices (2012 and later), though older Kindles require the MOBI format.
Frequently Asked Questions
What is AZW3 format?
Why convert EPUB to AZW3 instead of MOBI?
What devices support AZW3?
Can I convert DRM-protected EPUBs?
No. DRM-protected EPUB files (purchased from stores with copy protection) cannot be converted. You must remove DRM protection first using appropriate tools, or contact the publisher for a DRM-free version.
Will formatting be preserved?
Can I sideload AZW3 files to my Kindle?
How does AZW3 compare to Amazon's native Kindle format?
Can I use Send to Kindle with AZW3 files?
documents folder.Why does my Kindle show AZW3 files as 'documents'?
What are the limits for this converter?
| Tier | Max File Size | Max Files/Batch | Parallel Processing |
|---|---|---|---|
| Free | 50 MB | 50 files | 3 at once |
| Pro | 200 MB | 200 files | 6 at once |
| Business | 1024 MB | 1000 files | 10 at once |
Note: File size limits are specific to this converter. Batch and parallel processing limits apply to all ebooks converters site-wide. See all converter limits →
How are credits calculated for this conversion?
Cost: 1 credit per 10 MB
How it works:
- Files up to 10 MB: 1 credit (minimum)
- 11-20 MB: 2 credits
- 21-30 MB: 3 credits
- 31-40 MB: 4 credits
- Over 1024 MB: 103 credits (maximum cap)
Example: A 5 MB file = 1 credit. A 95 MB file = 10 credits.
Why per-megabyte? Larger files require more resources (processing, bandwidth, storage).
What are my daily and monthly credit limits?
Credit allocations vary by account tier:
| Tier | Daily Limit | Monthly Limit |
|---|---|---|
| Free | 50 credits/day | — |
| Pro | — | 10,000 credits/month |
| Business | — | 25,000 credits/month |
Daily credits (Free tier, including guests) reset every day at midnight UTC. Monthly credits (Pro & Business) reset on your billing cycle date.
Note: With 1 credit per 10 MB, images under 10 MB cost 1 credit each. Pro users can convert 10,000 images per month.
Answers at a Glance
Quick answers to common questions.
- Are my files secure?
- How long do you keep my files?
- What metadata do you keep?
- What happens after I drop a file?
- Why are conversions so fast?
- How do you measure performance?
- What are the exact limits for each plan?
- Can I process files in bulk?
- Why did my file fail to convert?
- Do you use my files to train AI?
Related Ebook Converters
Need a different format? Try these alternatives.
Choose Your Plan
Limits shown for EPUB to AZW3 conversion. One subscription unlocks the entire Tools.FAST Network. Plans cover Convert.FAST, Compress.FAST, PDF.FAST (soon), and all future tools.
Free
For occasional personal use
- 50 MB per file
- 50 files per batch
- 3 parallel standard conversions
- 2 parallel AI conversions
- 50 credits/day
- Standard priority
- Email support
No sign-up required.
Create an account for your own credit pool.
Pro
For independent work
- 200 MB per file
- 200 files per batch
- 6 parallel standard conversions
- 4 parallel AI conversions
- 10,000 credits/month across Tools.FAST
- High priority
- Email & chat support
- One subscription for the entire Tools.FAST network
Business
For production scale
- 1 GB per file
- 1000 files per batch
- 10 parallel standard conversions
- 6 parallel AI conversions
- 25,000 credits/month across Tools.FAST
- Add seats to invite team members
- Highest priority
- Priority email & chat support
- One subscription for the entire Tools.FAST network
How Credits Work
- Usually 1 credit per conversion. Exact cost shown before you start.
- Credits refresh monthly on your billing cycle.
- Unused credits roll over, capped at your plan's monthly amount.
- One subscription, all sites. Works across Convert.FAST, Compress.FAST, and future tools.
What's New in EPUB to AZW3
Latest improvements to this converter
Initial release of EPUB to AZW3 converter for modern Kindle devices.