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OTB to EPUB Converter

Quick OTB to EPUB conversion for e-reader compatibility

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Secure Processing

Uploaded OTB images are erased right after conversion, and the resulting EPUB files are purged within 24 hours — your data stays private.

Browser-Based Tool

No software to download — convert OTB to EPUB entirely in your web browser. Works on any device with an internet connection.

Simple Interface

Three steps to convert: upload your OTB, select EPUB, and download. The clean interface makes the process intuitive even for first-time users.

How to convert OTB to EPUB

1

Select files from Computer, Google Drive, Dropbox, URL or by dragging it on the page.

2

Choose epub or any other format you need as a result (more than 200 formats supported)

3

Let the file convert and you can download your epub file right afterwards

About formats

OTB (Over-the-Air Bitmap) is a monochrome image format developed by Nokia as part of their Smart Messaging specification in 1997, designed for transmitting small graphics — operator logos, group graphics, and picture messages — to Nokia mobile phones via SMS. OTB files contain 1-bit (black and white) images at small fixed resolutions, typically 72x14 pixels for operator logos and 72x28 pixels for group graphics, encoded in a compact binary format suitable for embedding within the payload of SMS text messages. The format uses a simple structure: a header byte indicating whether the image is an operator logo or group graphic, width and height values, and the raw bitmap data where each bit represents one pixel packed eight per byte. The extremely tight format — designed to fit within a single SMS message (140 bytes maximum payload, shared with addressing overhead) — reflects the severe constraints of mobile communication in the late 1990s. Nokia's Smart Messaging system was one of the first commercial implementations of rich content delivery to mobile phones, and OTB images represented the entire visual content capability of Nokia handsets before MMS and mobile data browsing arrived. One advantage is the format's historical role as a pioneer of mobile visual messaging: OTB images were among the first graphics that ordinary consumers could send to each other's phones, predating MMS, camera phones, and smartphones by nearly a decade. The format's minimal footprint is another characteristic — entire images fit in a few dozen bytes, reflecting an era of extreme bandwidth constraints. OTB files are supported by ImageMagick, various Nokia phone management tools, and specialty mobile format utilities.
Developer: Nokia
Initial release: 1997
EPUB (Electronic Publication) is an open ebook standard originally developed by the International Digital Publishing Forum (IDPF) and now maintained by the W3C following the organizations' merger in 2017. The first version carrying the EPUB name was approved in October 2007 as a successor to the Open eBook Publication Structure (OEBPS). An EPUB file is essentially a ZIP archive containing XHTML or HTML5 content documents, CSS stylesheets, images, fonts, and metadata organized according to the Open Packaging Format and Open Container Format specifications. The current major version, EPUB 3, supports reflowable and fixed-layout content, embedded multimedia, JavaScript interactivity, MathML equations, and rich accessibility features including semantic markup and media overlays for synchronized text and audio. A defining advantage is universal device support — unlike proprietary formats, EPUB works natively on virtually every non-Kindle e-reader, tablet, and reading application, from Apple Books and Google Play Books to Kobo and dozens of third-party apps. The reflowable text model is another core strength, automatically adapting pagination, font size, and margins to match any screen dimension and user preference. EPUB's open specification and active W3C stewardship ensure long-term preservation and vendor independence, making it the de facto standard for digital publishing across libraries, academic institutions, and commercial retailers worldwide.
Initial release: October 2007

Frequently Asked Questions

What is the reason to convert OTB to EPUB?

Converting OTB to EPUB packages your images for e-readers. EPUB is a reflowable e-book standard, making it suitable for portable reading devices.

What programs open EPUB files?

Open EPUB using Apple Books, Kobo, Calibre, Google Play Books. Cross-platform support means you can access these files on virtually any system.

Is OTB to EPUB conversion free?

Yes — Convertio offers free OTB to EPUB conversion. Premium options exist for users who need more capacity or faster processing speeds.

What platforms support this OTB converter?

Convertio is entirely web-based. Convert OTB to EPUB from Chrome, Firefox, Safari, Edge, or any modern browser on any operating system.

Does converting OTB to EPUB affect quality?

Quality is maintained to the extent EPUB supports. Since OTB is an Over-The-Air bitmap format for early Nokia phones, the visual data transfers cleanly to EPUB.

Can I convert multiple OTB files to EPUB at once?

Convertio supports batch mode — drag in multiple OTB files and they all convert to EPUB together, which is much faster than one-by-one.