CONVERT HTMLZ → TXTZ (HTMLZ to TXTZ)
Fast, secure HTMLZ to TXTZ conversion. No registration required.
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Studio Panel
Ghostscript + QPDFHOW TO CONVERT HTMLZ → TXTZ
Provide the HTMLZ
Select or drag your ebook up to 25 MB free (up to 2 GB with Kaiju Cloud). No account or library sign-in is required.
Run Calibre
Our pipeline runs the same Calibre command that powers desktop conversions, with device-appropriate defaults.
Retrieve the TXTZ
A download link appears when conversion completes. Metadata is preserved inside the TXTZ for library indexing.
Setup: HTMLZ is an ebook-family format used for digital reading on e-readers and reading apps. Goal: an interchangeable TXTZ. Converting HTMLZ to TXTZ is about reader compatibility more than anything else. Kindle hardware speaks TXTZ but not HTMLZ; Kobo reads TXTZ happily but stumbles on HTMLZ; third-party apps vary. This tool bridges the gap without asking you to install and learn Calibre yourself. In practice HTMLZ is an ebook-family format used for digital reading on e-readers and reading apps. On the other end, TXTZ is an ebook-family format used for digital reading on e-readers and reading apps.
Why convert HTMLZ to TXTZ
TXTZ reflows correctly on the small e-ink screens; some HTMLZ files are fixed-layout PDFs or early-generation ePubs that do not resize gracefully. Converting fixes the reading experience on 6-inch screens.
HTMLZ vs TXTZ — Technical specifications
Side-by-side comparison of the technical details.
HTMLZ
- MIME type
- application/x-htmlz
- Extension
- .htmlz
- Container
- ZIP + HTML
- Tool
- Calibre
- MIME Type
- application/htmlz
- Category
- eBooks
- Full Name
- HTMLZ eBook
- Conversion Engine
- CALIBRE
TXTZ
- MIME type
- application/x-txtz
- Extension
- .txtz
- Container
- ZIP + TXT
- Tool
- Calibre
- MIME Type
- application/txtz
- Category
- eBooks
- Full Name
- TXTZ eBook
- Conversion Engine
- CALIBRE
| Specification | HTMLZ | TXTZ |
|---|---|---|
| MIME type | application/x-htmlz | application/x-txtz |
| Extension | .htmlz | .txtz |
| Container | ZIP + HTML | ZIP + TXT |
| Tool | Calibre | Calibre |
| MIME Type | application/htmlz | application/txtz |
| Category | eBooks | eBooks |
| Full Name | HTMLZ eBook | TXTZ eBook |
| Conversion Engine | CALIBRE | CALIBRE |
HTMLZ vs TXTZ — Strengths and limitations
What each format does best, and where it falls short.
HTMLZ Strengths
- Simpler than EPUB.
- ZIP-of-HTML portability.
- Calibre-native.
Limitations
- Niche — no reader support.
- Not a mainstream delivery format.
- Calibre-only.
TXTZ Strengths
- Minimalist ebook wrapper.
- Plain-text core.
Limitations
- Niche.
- No reader adoption.
Quality & Compatibility
Cover images are re-embedded at the device-appropriate resolution, which may compress them more aggressively than the HTMLZ did. If you need pixel-perfect covers, override the cover image in Advanced to skip the re-encode.
Tips for Best Results
- Always keep the HTMLZ original until you have verified the TXTZ on the destination device — screenshots in a browser can look fine while e-ink rendering differs.
- For large libraries, batch-convert via a single ZIP upload; the job processes each ebook individually and returns a combined archive.
- Set the output profile (Kindle, Kobo, generic) in Advanced — defaults are sensible but a device-specific profile yields better reflow.
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 HTMLZ 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 HTMLZ 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 HTMLZ 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 HTMLZ 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.
HTMLZ eBook
Source formatHTMLZ is a zipped HTML ebook format used by Calibre as a lossless intermediate representation. It packages HTML content, CSS stylesheets, and images into a single ZIP archive, preserving full formatting fidelity during ebook conversion chains.
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 HTMLZ 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 HTMLZ.
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 HTMLZ 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.
HTMLZ vs TXTZ — Typical file sizes
Approximate file sizes for common scenarios.
- Typical novel 300 KB - 2 MB
- Novel (plain text) 200 KB - 1.5 MB
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