Convert G4 files online for free
The converter easily converts your G4 file to various formats - free and online. No Photoshop or extra software needed.
The converter also works in reverse, so you can convert other Raster Image formats to G4 with high quality output.
The .g4 extension primarily represents a CALS Group 4 raster image or a raw CCITT Group 4 fax stream. Originally standardized by the ITU-T and the US Department of Defense (CALS initiative), this format uses highly efficient lossless compression specifically designing for 1-bit monochrome documents like engineering diagrams, patent filings, and scanned faxes. A significant secondary use for this extension is an ANTLR v4 grammar file, a plain text format used by developers to describe language syntax.
Users frequently face difficulties with .g4 image files because they are effectively obsolete in consumer contexts. Most modern default image viewers (such as Windows Photos or macOS Preview) cannot decode raw G4 streams or handle the specific CALS headers, making the files appear broken or unrecognized. Additionally, the format is strictly limited to black and white, offering no support for grayscale or color data. For ANTLR files, the challenge is distinct: users often mistake them for executable scripts when they are actually definitions that must be compiled.
To ensure long-term accessibility for technical drawings and documents, convert image-based .g4 files to PDF for universal sharing or TIFF (which supports G4 compression natively) for archiving. For use on websites, PNG is the ideal target to maintain sharp lines without artifacts. If your file is text-based code, it is an ANTLR file; open it with a text editor or process it with the ANTLR Tool to generate parser code.
Use Convert.Guru to open and convert your G4 file.
Users also converted ICS, FNA, IGNORE and G3 files.
If you want to convert G4 file to WEBP, CUR or PSB, you can use XnView or similar software from the "Monochrome Raster Image Storage" category. In the File menu, look for Save As… or Export….
To convert RAW, PNG, AI, NEF, PSB, DNG, SVG, GIF, EPS, JPG, ARW or PDF files to G4, try XnView or another comparable tool in the "Monochrome Raster Image Storage" category.
The history of Convert.Guru began over 25 years ago in California with Tom Simondi’s file-format database. A former contributor to Space Shuttle development and a software pioneer of the 1980s, Simondi established a trusted resource for file type analysis that was even referenced by Microsoft Windows XP. Today, we use modern technology to process and convert thousands of file formats while continually improving our G4 converter.