PNG to OTB Converter

Convert PNG to OTB Nokia OTA bitmap format free

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Nokia Legacy

Create OTB operator logos and picture messages for vintage Nokia phones — a nostalgic format from the early mobile era.

Compact Bitmap

OTB produces tiny monochrome bitmaps optimized for legacy phone screens and SMS-based image delivery.

Online Conversion

No Nokia SDK or mobile development tools needed. Convert PNG to OTB directly through your web browser.

How to convert PNG 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

PNG (Portable Network Graphics) is a lossless raster image format developed by the PNG Development Group and published as a W3C Recommendation on October 1, 1996, created as a patent-free replacement for GIF after the Unisys LZW patent controversy. PNG uses a two-stage compression pipeline: a prediction filter selects the optimal per-row preprocessing (none, sub, up, average, or Paeth), then DEFLATE compression encodes the filtered data. The format supports rich color modes — 1/2/4/8/16-bit grayscale, 8/16-bit per channel true color, and indexed color with palettes up to 256 entries — all with optional alpha transparency ranging from a single transparent color to a full per-pixel alpha channel with 256 or 65536 levels. PNG also stores gamma correction, ICC color profiles, text metadata, and suggested background color. One advantage is lossless compression with transparency — PNG preserves every pixel exactly while supporting smooth semi-transparent edges, making it the standard format for web graphics, UI elements, logos, screenshots, and any image where artifacts or color shifts are unacceptable. Universal support is another core strength: every web browser, operating system, image editor, and programming library handles PNG natively. The format has proven remarkably durable — after nearly three decades, PNG remains the default lossless web image format. While newer formats like WebP and AVIF offer better compression, PNG's combination of lossless quality, full transparency, and absolute ubiquity keeps it indispensable.
Initial release: October 1, 1996
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 PNG to OTB?

OTB was used for sending operator logos and pictures to Nokia phones via SMS. Converting PNG creates images in this legacy mobile format.

What devices used OTB?

Legacy Nokia GSM phones (3310, 6110, etc.) received OTB images as operator logos, caller group logos, and picture messages.

What size should the PNG be?

Nokia operator logos were typically 72x14 pixels. Scale your PNG to match the target phone model requirements.

Is PNG to OTB free?

Yes — conversion is free on Convertio. Premium users get batch processing for creating multiple OTA bitmaps.

Is OTB monochrome?

Yes — OTB stores monochrome (1-bit) images. Your PNG is converted to black and white for the Nokia phone display.

Is OTB still relevant?

OTB is a legacy format for vintage Nokia phones. It is mainly of interest to retro mobile enthusiasts and collectors.

PNG to OTB Quality Rating

4.6 (14 votes)
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