OTB to GRAY Converter
Processing entirely on your device — large files may take a moment.
Convert GRAY dumps exactly like GRAYA — to PNG or JPG with width hints. If your files are still in OTB format, this page is the shortcut: OTB is the Nokia OTA Bitmap — 1-bit monochrome images that old Nokia phones displayed as operator logos and picture messages.
This converter runs entirely in your browser using WebAssembly — your files never leave your device, nothing is uploaded, and there are no watermarks, sign-ups or queues. Drop in several files at once to convert them as a batch.
How OTB compares to GRAY
| OTB | GRAY | |
|---|---|---|
| Structure | Nokia OTA Bitmap coder | Grayscale + Alpha (raw) coder |
| Compatibility | ImageMagick, specialty tools | ImageMagick, specialty tools |
| Best for | Legacy and specialty pipelines | Legacy and specialty pipelines |
How to convert OTB to GRAY
- 1
Select your files
Drag & drop your OTB files onto the area above, or click to browse. You can add multiple files at once for batch conversion.
- 2
Convert instantly
Click "Convert to GRAY". The conversion runs entirely inside your browser using WebAssembly — no upload, no queue, no waiting.
- 3
Download results
Download each converted GRAY file individually, or grab everything at once as a ZIP archive.
About the OTB format
The Nokia OTA Bitmap coder of the ImageMagick set — the retro-phone format is written natively by the magick.wasm engine, entirely in your browser.
Obscure coder formats like this are exactly what template-driven converters list and never actually convert — here it really works.
+Strengths
- ✓Written natively by ImageMagick
- ✓Runs entirely in your browser
- ✓Free, private, no watermarks
!Limitations
- −Niche format — few modern readers
- −Feature subset varies by coder
- −Keep the original for re-editing
About the GRAY format
The Grayscale + Alpha (raw) coder of the ImageMagick set — the raw-pixels format is written natively by the magick.wasm engine, entirely in your browser.
Obscure coder formats like this are exactly what template-driven converters list and never actually convert — here it really works.
+Strengths
- ✓Written natively by ImageMagick
- ✓Runs entirely in your browser
- ✓Free, private, no watermarks
!Limitations
- −Niche format — few modern readers
- −Feature subset varies by coder
- −Keep the original for re-editing
Why convert OTB to GRAY?
There is a concrete reason this conversion exists: Niche format — few modern readers GRAY sidesteps that — Written natively by ImageMagick If that is your situation, the tool above settles it in seconds, entirely on your device.
Frequently asked questions
Is this OTB to GRAY converter really free?
Yes — completely free, with no sign-up, no watermark and no daily conversion limits. The site is supported by advertising.
Are my files uploaded to a server?
No. The conversion runs entirely inside your browser using WebAssembly, so your files never leave your device — that is what makes it instant and private.
Does it work on Windows, Mac, iPhone and Android?
Yes. Anything with a modern browser works: Windows, macOS, Linux, Android and iOS. No software installation is required.
Will I lose quality converting OTB to GRAY?
No — GRAY is a lossless format, so every pixel of the converted image matches your original OTB file. You can also adjust the quality/size balance before converting when the target format supports compression.
Will transparent areas survive the conversion to GRAY?
Transparency is kept whenever GRAY actually supports an alpha channel. If the target format has none (like JPG), transparent areas are flattened onto a white background — that is a property of the format, not of this tool.
What happens to EXIF data and other metadata?
Conversions here re-encode the image, and re-encoding generally does not carry the original metadata over. If the EXIF data of your OTB files matters (camera model, GPS, timestamps), keep the original file as the master and treat the converted copy as the shareable version.