OTB to SK Converter

Online OTB to SK — from bitmap to vector in seconds

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Effortless Process

Converting OTB to SK takes just a few clicks — no technical knowledge required. Upload, choose your format, and download the result.

Any Device Works

Convert OTB to SK from Windows, macOS, Linux, or mobile — the browser-based tool adapts to any screen size and operating system.

Secure Processing

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

How to convert OTB to SK

1

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

2

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

3

Let the file convert and you can download your sk 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
SK is the native file format of Skencil (originally named Sketch), a free vector graphics editor for Linux created by Bernhard Herzog, with the first public release on October 31, 1998. Skencil holds historical significance as one of the earliest full-featured vector drawing applications written almost entirely in Python, with only performance-critical rendering components implemented in C. The SK file format uses a text-based, Python-like syntax to describe document structure — pages, layers, groups, and individual graphic objects are represented as nested statements with parameters specifying coordinates, colors, line styles, and transformations. The format supports Bezier curves, rectangles, ellipses, text objects with font specifications, imported raster images, gradient and pattern fills, and hierarchical grouping with affine transforms. One advantage is human readability — SK files can be opened in any text editor, making it possible to inspect, modify, or generate artwork programmatically using simple scripts. The Python-native structure also provides a benefit for automation: since Skencil itself is a Python application, the file format integrates naturally with scripting workflows for batch processing and procedural graphic generation. While Skencil's development slowed after the mid-2000s, its SK format became the foundation for the sK1 project, which extended the format and continued active open-source vector graphics development. SK files remain convertible through sK1, UniConvertor, and other open-source tools.
Developer: Bernhard Herzog
Initial release: October 31, 1998

Frequently Asked Questions

Why convert OTB to SK?

OTB is a legacy raster format from Nokia mobile phones. Converting to SK gives you Sketch/Skencil vector drawing format — ideal for scalable graphics that stay sharp at any size.

What programs open SK files?

Open SK using Skencil, Inkscape (with import), UniConvertor. Cross-platform support means you can access these files on virtually any system.

Are my uploaded files kept private?

Yes — your OTB files are deleted immediately after processing. The resulting SK files are also removed from servers within 24 hours.

Is OTB to SK conversion free?

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

Does this converter work on mobile devices?

It works on any device with a web browser. Whether you are on Android, iOS, Windows, or macOS — OTB to SK conversion is fully supported.

Can I convert multiple OTB files to SK at once?

Absolutely. Batch upload your OTB images and convert them all to SK in a single pass — no need to repeat the process for each file.