CONVERT HTMLZ → LRF (HTMLZ to LRF)
Fast, secure HTMLZ to LRF conversion. No registration required.
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Studio Panel
Ghostscript + QPDFHOW TO CONVERT HTMLZ → LRF
Start the job
Upload a HTMLZ; we read metadata, cover image and table of contents from the source container.
Rewrite as LRF
The content is flowed into the LRF format with appropriate CSS, images re-encoded at recommended dimensions.
Save the ebook
Download the LRF. Side-load to your device or drop into your reader library.
Setup: HTMLZ is an ebook-family format used for digital reading on e-readers and reading apps. Goal: an interchangeable LRF. Going from HTMLZ to LRF preserves the book structure — ToC, chapters, cover image, bold/italic runs, embedded fonts where licensing permits — and emits a LRF file that reflows correctly on small screens. The pipeline handles the CSS remapping and image re-encoding automatically. Keep in mind HTMLZ is an ebook-family format used for digital reading on e-readers and reading apps. And remember that LRF is Sony's BBeB legacy ebook format for the original Sony Reader.
Why convert HTMLZ to LRF
Library applications (Calibre, Apple Books, Kindle library) prefer a single format for indexing. Converting mixed HTMLZ/LRF collections to one canonical LRF makes search, filter and sync work reliably.
HTMLZ vs LRF — 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
LRF
- MIME type
- application/x-sony-bbeb
- Extension
- .lrf
- MIME Type
- application/x-sony-bbeb
- Category
- eBooks
- Full Name
- Sony LRF eBook
- Conversion Engine
- CALIBRE
- Native reader
- Sony PRS series (retired 2014)
| Specification | HTMLZ | LRF |
|---|---|---|
| MIME type | application/x-htmlz | application/x-sony-bbeb |
| Extension | .htmlz | .lrf |
| Container | ZIP + HTML | — |
| Tool | Calibre | — |
| MIME Type | application/htmlz | application/x-sony-bbeb |
| Category | eBooks | eBooks |
| Full Name | HTMLZ eBook | Sony LRF eBook |
| Conversion Engine | CALIBRE | CALIBRE |
| Native reader | — | Sony PRS series (retired 2014) |
HTMLZ vs LRF — 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.
LRF Strengths
- Sony PRS-native.
- Rich layout.
- Calibre-readable.
Limitations
- Deprecated.
- Sony exited the market.
- No new content.
Quality & Compatibility
DRM-protected HTMLZ files cannot be converted — KaijuConverter respects publisher encryption and returns an error rather than stripping protection. Unprotected or self-published HTMLZ ebooks convert without restriction.
Tips for Best Results
- Use structure detection (TOC > chapters) to regenerate a clean table of contents in the LRF if the HTMLZ 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 LRF cover rather than auto-generating per HTMLZ.
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 LRF. 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 LRF 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 LRF 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.
Sony LRF eBook
Target formatLRF (BBeB Book) is a proprietary ebook format developed by Sony for their Reader line of e-ink devices. It supports reflowable text, images, and basic formatting, but has been superseded by EPUB on newer Sony Reader models.
Going the other way? Convert LRF back to HTMLZ with the same engine.
Common Use Cases
Share across platforms
Send LRF files to anyone without worrying about whether they have the right software for HTMLZ.
Embed in documents
Drop LRF output into Word, Google Docs, PowerPoint, Notion or a website without conversion warnings.
Optimize size
LRF 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 LRF — Typical file sizes
Approximate file sizes for common scenarios.
- Typical novel 300 KB - 2 MB
- Typical novel 500 KB - 3 MB
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