G3 (Group 3) is a fax image format using ITU-T T.4 compression, the standard for document facsimile transmission.
OTB is a bitmap format for mobile devices, used for operator logos and graphics sent via SMS.
FreeFileConvert uses tuned encoding for G3 to OTB conversions, preserving clarity while trimming file size. Finished audio streams instantly across phones, tablets, desktops, and modern browsers without extra tweaks.
Upload G3 files from desktop, tablet, or cloud storage, queue multiple jobs, and let the converter finish autonomously. Return whenever convenient to download synchronized OTB results on any device you rely on.
Process up to 5 files sized 1000 MB per batch without splitting queues manually. Mixed-format uploads convert together, producing consistent OTB audio with dependable progress tracking.
G3 uses Modified Huffman (MH) run-length encoding optimized for black-and-white documents.
OTB images are small monochrome bitmaps optimized for mobile transmission.
Upload your image file in the G3 format from your device, Dropbox, or Google Drive.
Select OTB as the output format and click Convert. Adjust optional settings if needed.
Download the converted image file. Each file stays available for up to 5 downloads.