CONVERT MOBI → TXTZ (MOBI to TXTZ)
Fast, secure MOBI to TXTZ conversion. No registration required.
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Studio Panel
Ghostscript + QPDFHOW TO CONVERT MOBI → TXTZ
Start the job
Upload a MOBI; we read metadata, cover image and table of contents from the source container.
Rewrite as TXTZ
The content is flowed into the TXTZ format with appropriate CSS, images re-encoded at recommended dimensions.
Save the ebook
Download the TXTZ. Side-load to your device or drop into your reader library.
Situation. MOBI is Amazon's legacy Mobipocket ebook format, the older Kindle delivery format. Solution: a TXTZ, produced below. Going from MOBI to TXTZ preserves the book structure — ToC, chapters, cover image, bold/italic runs, embedded fonts where licensing permits — and emits a TXTZ file that reflows correctly on small screens. The pipeline handles the CSS remapping and image re-encoding automatically. Worth knowing: MOBI is Amazon's legacy Mobipocket ebook format, the older Kindle delivery format. Meanwhile TXTZ is an ebook-family format used for digital reading on e-readers and reading apps.
Why convert MOBI to TXTZ
Library applications (Calibre, Apple Books, Kindle library) prefer a single format for indexing. Converting mixed MOBI/TXTZ collections to one canonical TXTZ makes search, filter and sync work reliably.
MOBI vs TXTZ — Technical specifications
Side-by-side comparison of the technical details.
MOBI
- MIME type
- application/x-mobipocket-ebook
- Extension
- .mobi, .prc (PalmDOC variant)
- Container
- Palm Database (PDB)
- Markup
- Compressed HTML subset
- Successor
- .azw, .azw3 (Kindle-specific)
- MIME Type
- application/x-mobipocket-ebook
- Category
- eBooks
- Full Name
- Mobipocket eBook
- Conversion Engine
- CALIBRE
TXTZ
- MIME type
- application/x-txtz
- Extension
- .txtz
- Container
- ZIP + TXT
- MIME Type
- application/txtz
- Category
- eBooks
- Full Name
- TXTZ eBook
- Conversion Engine
- CALIBRE
- Tool
- Calibre
| Specification | MOBI | TXTZ |
|---|---|---|
| MIME type | application/x-mobipocket-ebook | application/x-txtz |
| Extension | .mobi, .prc (PalmDOC variant) | .txtz |
| Container | Palm Database (PDB) | ZIP + TXT |
| Markup | Compressed HTML subset | — |
| Successor | .azw, .azw3 (Kindle-specific) | — |
| MIME Type | application/x-mobipocket-ebook | application/txtz |
| Category | eBooks | eBooks |
| Full Name | Mobipocket eBook | TXTZ eBook |
| Conversion Engine | CALIBRE | CALIBRE |
| Tool | — | Calibre |
MOBI vs TXTZ — Strengths and limitations
What each format does best, and where it falls short.
MOBI Strengths
- Universal Kindle support on every device ever released.
- Very small file sizes for text-heavy books.
- Mature tooling via Calibre and Amazon's KindleGen.
- Simple container structure — easy to parse.
Limitations
- Deprecated by Amazon for new uploads since 2022.
- Poor support for rich typography (drop caps, ligatures, fixed layout).
- No embedded fonts in the base format.
TXTZ Strengths
- Minimalist ebook wrapper.
- Plain-text core.
Limitations
- Niche.
- No reader adoption.
Quality & Compatibility
DRM-protected MOBI files cannot be converted — KaijuConverter respects publisher encryption and returns an error rather than stripping protection. Unprotected or self-published MOBI ebooks convert without restriction.
Tips for Best Results
- Use structure detection (TOC > chapters) to regenerate a clean table of contents in the TXTZ if the MOBI has none.
- Embedded fonts bloat file size — consider dropping them in Advanced if your reader uses its own typography anyway.
- For serialised fiction, keep cover art consistent across episodes by re-using one TXTZ cover rather than auto-generating per MOBI.
Frequently Asked Questions
Yes. The free tier accepts files up to 25 MB without registration, email capture or watermarks; paid plans go up to 2 GB. Paid plans raise the size cap, enable batch conversions and provide a REST API for automation, but nothing on the free tier is quality-limited — the output is exactly the same as on any paid plan.
Yes, provided the MOBI itself has a well-formed ToC. Calibre reads the navigation structure and writes an equivalent ToC into the TXTZ. If the source lacks a ToC we can generate one from heading levels in Advanced → structure detection.
Uploads run over HTTPS, files are processed in isolated containers, and both the source MOBI and the TXTZ output are auto-deleted within two hours. No account is required, file contents are never logged, and KaijuConverter does not use uploads for AI training. The paid plan adds a signable data-processing agreement for regulated workflows.
No. KaijuConverter does not strip digital rights management. DRM-free MOBI files — anything you authored yourself, public-domain classics, files from DRM-free retailers — convert without any restriction.
Most files finish in well under a minute. Small images and documents are typically ready in a few seconds; large video or audio files scale roughly with duration. Upload speed from your network is usually the dominant factor, not server time.
Yes. The cover is extracted from the MOBI and re-embedded in the TXTZ at device-appropriate dimensions. You can also override it in Advanced by uploading a custom cover image alongside the book file.
Mobipocket eBook
Source formatMOBI is the Mobipocket eBook format historically used by Amazon Kindle devices. While Amazon has moved to newer formats, MOBI remains relevant for older Kindles and legacy eBook libraries.
TXTZ eBook
Target formatTXTZ is a zipped plain text ebook format used by Calibre that packages a text file with optional metadata into a ZIP archive. It provides a lightweight ebook container when rich formatting is not required.
Going the other way? Convert TXTZ back to MOBI with the same engine.
Common Use Cases
Share across platforms
Send TXTZ files to anyone without worrying about whether they have the right software for MOBI.
Embed in documents
Drop TXTZ output into Word, Google Docs, PowerPoint, Notion or a website without conversion warnings.
Optimize size
TXTZ often produces smaller files than MOBI for web, email and storage.
Archive & future-proof
Store in a widely-supported format that will still open on future operating systems without legacy plugins.
MOBI vs TXTZ — Typical file sizes
Approximate file sizes for common scenarios.
- Text-only novel 200 KB - 1 MB
- Illustrated book 2-10 MB
- Novel (plain text) 200 KB - 1.5 MB
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Related comparisons
See these formats side by side to understand which fits your use case best.
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