SIX to OTB Converter

Transform SIX images into lossless OTB online

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Private & Secure

Your SIX uploads are deleted right after conversion, and the OTB output is removed from servers within 24 hours — your data stays safe.

Cloud Processing

Conversion runs on remote servers, so your computer stays fast. Even large SIX images are handled without slowing your device.

Retro Graphics Export

SIX encodes images for vintage DEC terminals. Converting to OTB extracts that artwork into a format modern tools understand.

How to convert SIX to OTB

1

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

2

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

3

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

About formats

SIX is a file extension for SIXEL (Six Pixel) graphics data, a bitmap graphics format developed by Digital Equipment Corporation (DEC) in 1983 and introduced with the LA50 dot matrix printer. SIXEL encodes images as a sequence of printable ASCII characters, where each character represents a column of six vertical pixels (a 'sixel') — the character's ASCII value minus 63 provides a 6-bit binary pattern, with each bit controlling one pixel in the vertical column. The encoding is structured as a series of sixel bands (each six pixels tall) across the image width, with control sequences for color selection (up to 256 registers with HLS or RGB specification), repeat counts (run-length encoding for efficiency), carriage return, and newline commands. SIXEL data is transmitted to the output device using DEC's standard escape sequence protocol, embedded within the text stream alongside regular character output. Originally designed for DEC's line of printers and later supported by DEC VT-series terminals (VT240, VT330, VT340), SIXEL has experienced a remarkable revival in modern terminal emulator software. One advantage is terminal-native image display: SIXEL allows images to be rendered directly within a text terminal session without requiring a graphical window system, enabling command-line tools to display graphs, photographs, and previews inline with text output. This capability has driven adoption in modern terminals like mlterm, xterm, WezTerm, and foot. SIX/SIXEL data can be generated by ImageMagick, libsixel, and chafa, and viewed in any SIXEL-capable terminal emulator.
Initial release: 1983
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

Frequently Asked Questions

Why convert SIX to OTB?

DEC SIX terminal images cannot be opened in regular image viewers. Converting to OTB preserves the artwork in a portable form.

What programs can open OTB?

Nokia phones originally displayed OTB images. ImageMagick and specialized mobile graphics tools can open OTB bitmap files today.

Does SIX to OTB preserve quality?

OTB preserves image data without lossy compression, so the visual content from your SIX is retained faithfully during conversion.

Is SIX to OTB conversion fast?

The process is fast — cloud-based processing handles SIX to OTB conversion in seconds for standard-sized images, even on slower connections.

Does Convertio support batch SIX to OTB conversion?

Absolutely. Add several SIX images at once, set OTB as the output, and the converter processes them all in parallel for maximum efficiency.