G3 to PGX Converter

Free G3 to PGX conversion — browser-based tool

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Private & Secure

Uploaded G3 files are erased right after conversion. PGX results are automatically deleted within 24 hours.

Fax to Digital

Bridge the gap between legacy G3 encoding and PGX — preserve and modernize your fax document archive.

Nothing to Install

The G3 to PGX conversion happens in your browser — no software to download or configure on your device.

How to convert G3 to PGX

1

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

2

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

3

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

About formats

G3 is a monochrome image format based on the ITU-T Group 3 facsimile coding standard (Recommendation T.4), ratified by the CCITT in 1980 as the universal compression method for fax transmission over telephone networks. G3 files contain 1-bit (black and white) image data encoded using Modified Huffman (MH) one-dimensional coding, where each scanline is independently compressed by replacing runs of consecutive white or black pixels with variable-length codewords from a predefined Huffman table optimized for typical document content. The standard also defines an optional two-dimensional coding mode (Modified READ) that encodes each line as differences from the previous line, achieving better compression for pages with vertical redundancy. Standard G3 resolution is 204 pixels per inch horizontally and either 98 (standard) or 196 (fine) pixels per inch vertically, producing the characteristic slightly-stretched appearance of received fax documents. The encoding was carefully optimized for the real-time transmission constraints of 1980s modems operating at 2400 to 14400 bps, where encoding and decoding speed had to match the communication channel rate. One advantage is universal telecommunications compatibility: Group 3 encoding remains the mandatory baseline codec for every fax machine manufactured, ensuring that G3 image data can be transmitted to or received from any fax device worldwide. The format's efficiency for document content is another strength — the Huffman tables were statistically tuned to the run-length distributions found in business documents, and typical pages compress to under 30 KB. G3 files are supported by LibreOffice, ImageMagick, and fax server software.
Developer: ITU-T (CCITT)
Initial release: 1980
PGX is a simple single-component raster image format defined as part of the JPEG 2000 standard (ISO/IEC 15444) for use in conformance testing and verification of JPEG 2000 codec implementations. Introduced around 2000 alongside the JPEG 2000 specification itself, PGX files store a single image component (one color channel or grayscale plane) with a text header followed by raw pixel data, providing an unambiguous reference representation against which encoder and decoder outputs can be compared sample by sample. The header is a single ASCII line specifying endianness (ML for big-endian, LM for little-endian), signedness (+ for unsigned, - for signed), bit depth (1 to 32 bits), width, and height. The pixel data follows as raw binary values, each occupying the minimum number of bytes needed for the specified bit depth, with one value per pixel. For multi-component images (like RGB), each component is stored in a separate PGX file. The format's deliberate simplicity — no compression, no metadata, no multi-channel support — ensures there are no ambiguities in interpretation that could mask codec bugs. One advantage is verification precision: PGX's uncompressed, exactly-specified representation allows bit-exact comparison of decoded JPEG 2000 output against reference images, essential for certifying that a codec implementation conforms to the standard. The format's role in the JPEG 2000 conformance testing framework means it is implemented by every serious JPEG 2000 codec (OpenJPEG, Kakadu, etc.) and used in the official ISO conformance test suite. PGX files can also be processed by ImageMagick and various JPEG 2000 development tools.
Initial release: 2000

Frequently Asked Questions

Why convert G3 to PGX?

G3 files require specialized fax viewers. Converting to PGX lets anyone open the content easily.

How do I view a PGX file?

Use OpenJPEG tools, ImageMagick, or JPEG 2000 reference software to view PGX files.

Will my G3 content stay sharp in PGX?

Full resolution is preserved during G3 to PGX conversion. Text and graphics remain sharp and clear.

Is there a charge for G3 to PGX?

Basic conversions are free. Premium subscriptions provide priority processing and expanded daily capacity.

Can I process many G3 files in one go?

Absolutely — add several G3 files at once. Each gets its own PGX conversion and individual download link.

Do I need to install any software?

No installations needed. The G3 to PGX conversion runs entirely in your browser — nothing to download or set up.