WMF to OTB Converter

WMF to OTB — on-the-air bitmap, free conversion

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Feature-Phone Graphics

Convert WMF to OTB — the monochrome bitmap format designed for feature phones and mobile devices.

Instant Delivery

OTB files are tiny, so the WMF conversion completes almost instantly on cloud servers.

Browser-Only Tool

No installs or plugins needed. Open Convertio in any browser to convert WMF to OTB.

How to convert WMF 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

WMF (Windows Metafile) is a vector graphics format created by Microsoft, introduced with Windows 3.0 in May 1990 as the platform's native format for recording and replaying graphical operations. A WMF file captures a sequence of GDI (Graphics Device Interface) drawing commands — lines, rectangles, ellipses, polygons, text, and bitmap blits — in the order they were issued, serializing screen or printer output into a replayable file. The format uses a 16-bit coordinate space and organizes records as a linear stream of function calls with their parameters, preceded by a header specifying the bounding rectangle and resolution. WMF became deeply integrated into the Windows ecosystem as the default format for clip art collections, Office document graphics, and clipboard vector interchange during the 1990s — Microsoft Office shipped with thousands of WMF clip art images that defined a visual era of desktop publishing. One advantage is pervasive compatibility: virtually every Windows application from the past three decades can render WMF content, making it one of the most widely supported vector formats in existence. The lightweight recording model is another strength — WMF files are compact and render quickly because they replay native system drawing calls rather than interpreting a complex graphics language. While 16-bit limitations and lack of transparency and Bezier curves led Microsoft to develop EMF as a 32-bit replacement, WMF files remain ubiquitous in legacy documents and across current Windows software.
Developer: Microsoft
Initial release: May 22, 1990
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 WMF to OTB?

OTB (On-The-Air Bitmap) is a monochrome format used by older Nokia and feature phones. Converting WMF to OTB creates graphics for these devices.

What reads OTB files?

Older Nokia phones, feature phone emulators, and image tools like ImageMagick can handle OTB format.

Is OTB a color format?

No — OTB is monochrome. The WMF color data is reduced to black-and-white during conversion.

Is this free?

Yes — WMF to OTB conversion is free on Convertio. Premium plans offer extra processing power.

How long does it take?

Almost instant. OTB files are tiny and cloud processing is extremely fast.

Can I batch-convert WMF to OTB?

Yes. Upload multiple WMF files and convert them all to OTB at once.