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Supported Formats
Convert between all major file formats with high quality
Web Formats
Joint Photographic Experts Group - the most universal image format for photographs using lossy compression. Reduces file sizes 90-95% with minimal visible quality loss. No transparency support. Perfect for photos, web images, email attachments, and any scenario requiring small file sizes. Adjustable quality levels from 1-100. Standard since 1992 with universal device and software support. Ideal for photographs and complex images with many colors.
Portable Network Graphics - lossless image format supporting transparency and 16 million colors. Larger files than JPEG but perfect quality preservation. Supports alpha channel for smooth transparency. Excellent for logos, graphics with text, screenshots, and images requiring transparency. Better compression than GIF for photos. Perfect for web graphics, UI elements, and any image needing lossless quality or transparency. Standard format for web graphics since 1996.
Web Picture format - modern image format by Google providing 25-35% smaller files than JPEG at equivalent quality. Supports both lossy and lossless compression plus transparency. Superior compression algorithms reducing bandwidth usage. Native browser support (96%+ coverage). Perfect for website optimization, web images, and reducing page load times. Combines best features of JPEG, PNG, and GIF. Recommended for modern web development.
Graphics Interchange Format - image format supporting animation and transparency with 256-color limitation. Small file sizes for simple images. Perfect for simple animations, emojis, memes, and graphics with few colors. Lossless for limited palette. Inefficient for photographs (use JPEG) or high-color graphics (use PNG). Universal support since 1987. Standard format for simple web animations and reaction images.
Scalable Vector Graphics - XML-based vector format rendering perfectly at any size. Infinitely scalable without quality loss or pixelation. Small file sizes for geometric shapes and illustrations. Editable with text editors and design software. Perfect for logos, icons, diagrams, and graphics requiring scaling. Supports animation and interactivity. Standard for responsive web graphics and resolution-independent designs. Essential format for modern web icons.
Icon File Format - specialized format for Windows icons containing multiple image sizes (16x16 to 256x256 pixels). Single file provides icons for all display resolutions. Used for favicons, application icons, and Windows shell icons. Supports transparency and multiple color depths. Perfect for website favicons, Windows program icons, and shortcut icons. Standard format for Windows icons since Windows 1.0. Essential for professional Windows applications.
AV1 Image File Format - next-generation image format based on AV1 video codec providing better compression than WebP and JPEG. 20-50% smaller files at equivalent quality. Supports HDR, wide color gamut, and transparency. Cutting-edge compression technology. Growing browser support (85%+ and increasing). Perfect for future-proof web images and maximum efficiency. Better quality at smaller sizes than any previous format. Recommended for modern websites prioritizing performance.
Bitmap Image File - uncompressed raster format from Microsoft providing pixel-perfect quality with large file sizes. No compression means huge files (1MB+ for screenshots). Fast to load and display. Simple format with universal Windows support. Perfect for temporary graphics, screen captures, and scenarios where compression artifacts are unacceptable. Legacy format largely replaced by PNG. Convert to PNG or JPEG for practical use and storage.
Tagged Image File Format - flexible format supporting multiple pages, layers, and various compression methods. Industry standard for professional photography, publishing, and archival. Supports lossless compression, 16-bit color depth, and extensive metadata. Large file sizes but excellent quality. Perfect for print publishing, photo archival, professional photography, and scenarios requiring maximum quality and flexibility. Used in medical imaging and professional scanning.
Professional Formats
Photoshop Document - Adobe Photoshop's native format preserving layers, effects, masks, and all editing capabilities. Supports 16-bit and 32-bit color depths for professional work. Large file sizes due to layer data and editing information. Perfect for ongoing design projects, professional photo editing, and collaborative design work. Not suitable for final output (export to JPEG/PNG). Essential format for professional graphic design and photo manipulation workflows. Industry standard for design files.
OpenEXR - high dynamic range image format developed by Industrial Light & Magic for visual effects and animation. Stores 16-bit or 32-bit floating-point values per channel enabling enormous dynamic range. Supports multiple layers, arbitrary channels, and lossless/lossy compression. Industry standard for VFX, CGI, and professional 3D rendering. Perfect for HDR photography, compositing, and scenarios requiring maximum color precision. Used extensively in film production and high-end visual effects.
High Dynamic Range Image - format storing luminance and color information with greater range than standard images. Captures and displays brightness levels impossible in JPEG/PNG. Uses 32-bit floating-point encoding. Perfect for realistic lighting in 3D rendering, environment maps, and HDR photography. Common in game development and architectural visualization. Enables realistic tone mapping and exposure adjustment. Essential for professional lighting workflows.
DirectDraw Surface - Microsoft texture format for games and 3D applications supporting compressed textures and mipmaps. Optimized for GPU loading with hardware-accelerated decompression. Stores multiple resolution levels (mipmaps) in single file. Standard format for game textures (DirectX, Unity, Unreal). Supports various compression algorithms (DXT1, DXT5, BC7). Perfect for game development, 3D modeling, and real-time rendering. Essential format for game asset pipelines.
Truevision TGA/Targa - raster graphics format supporting 8-32 bits per pixel with alpha channel. Uncompressed or RLE compressed for fast loading. Standard format for video editing, animation, and texture mapping. Excellent color accuracy with optional lossless compression. Perfect for video frame sequences, animation frames, and game textures. Widely supported in 3D software and video editing applications. Reliable format for professional media production.
JPEG 2000 - advanced image format using wavelet compression providing better quality than JPEG at equivalent file sizes. Supports lossless and lossy compression, progressive decoding, and ROI coding. Used in medical imaging, digital cinema, and archival. Better compression artifacts than JPEG. Slower encoding/decoding. Perfect for medical imaging, digital preservation, and applications requiring superior compression. Limited web browser support.
JPEG Stereo - stereoscopic 3D image format storing left and right eye views side-by-side or top-bottom. Based on standard JPEG with special arrangement for 3D viewing. Used for 3D photography, VR content, and stereoscopic displays. Compatible with 3D TVs and VR headsets. Perfect for 3D photography, stereoscopic content creation, and VR/AR applications. Requires special viewing equipment for proper 3D effect.
Portable Float Map - floating-point image format storing HDR color data. Simple format with 32-bit float values per channel. Used in computer graphics for HDR images and height maps. Uncompressed format with large file sizes. Perfect for HDR photography processing, displacement maps, and scientific imaging. Common in 3D rendering and simulation applications. Alternative to OpenEXR for simple HDR storage.
Flexible Image Transport System - scientific image format used primarily in astronomy. Stores astronomical images with extensive metadata headers. Supports multiple data arrays and tables. Standard format for astronomical data archives. Perfect for astronomical imaging, scientific data exchange, and research applications. Used by major observatories and space agencies worldwide. Essential format for astronomical research and data sharing.
How to Convert Files
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Frequently Asked Questions
What is a G3 file and why was this format created?
A G3 file is an image encoded using the CCITT Group 3 fax compression standard. It was created specifically for early fax machine transmissions, where bandwidth was extremely limited and phone line quality was inconsistent. Group 3 compression converts scanned documents into highly compact, 1-bit monochrome images while remaining resilient against noise from analog telephone systems.
G3 became the global standard for fax pages because it allowed fast transmission of text documents over low-quality phone lines. Today, G3 survives in fax archives, legacy telecom systems, and digital fax gateways, as well as inside TIFF-G3 images used by enterprise scanners.
How is a G3 file structured internally?
The G3 format uses a highly efficient encoding system tailored to monochrome documents:
1-bit Black-and-White Pixels
Each pixel is either black or white, enabling extremely small file sizes ideal for phone-based transmission.
Run-Length Encoding (RLE)
Group 3 stores alternating runs of black and white pixels using compact codes instead of storing every pixel individually.
Modified Huffman or Modified READ
Two modes exist: 1D Modified Huffman and 2D Modified READ, the latter improving compression by referencing previous lines.
Fixed Fax Resolutions
Standard fax sizes include 1728 pixels per line for A4 and letter-sized pages at 200 dpi.
Its simplicity and tight optimization reflect the technological constraints of early facsimile transmission.
Where are G3 files used today?
Despite being a legacy format, G3 still appears across multiple industries:
Fax Gateways and Digital Fax Servers
VoIP fax modules and SIP systems frequently store or transmit raw G3 streams internally.
Enterprise Document Scanners
Many document scanners support TIFF-G3 output for ultra-small, archivable black-and-white documents.
Medical, Legal, and Government Offices
Regulated institutions often store decades of faxed pages in G3 for authenticity and compliance.
Telecommunications Infrastructure
Old telecom nodes handle G3 fax decoding even today when routing faxes over PSTN or FoIP.
Corporate Fax Archives
Millions of stored fax transmissions remain encoded in G3 format across archival systems.
Embedded Fax Hardware
Multifunction printers and legacy fax systems still produce G3 as part of their pipeline.
Low-Bandwidth Document Transmission
G3 remains useful where bandwidth is extremely limited, such as in rural or satellite communication setups.
While niche today, G3 remains relevant in any environment requiring fax compatibility.
Why do some G3 files appear low-resolution or blocky?
G3 supports only 1-bit monochrome, so any shading, grayscale, or fine detail is lost during scanning.
Fax lines originally operated at limited resolutions like 200×100 or 200×200 dpi, causing visible jaggedness.
Older fax machines often introduced noise, creating speckles or broken characters in the resulting G3 image.
How does G3 differ from G4, TIFF-G3, and FAX formats?
G3 uses 1D or 2D compression, while G4 is more advanced and provides even better compression with 2D-only methods.
TIFF-G3 embeds G3-encoded data inside a TIFF container, adding metadata and multi-page support.
FAX bitmaps are raw fax images, while G3 is the underlying compression standard that many fax formats use.
Does the G3 format support grayscale, color, or transparency?
No-G3 only supports 1-bit black and white pixels.
There is no support for grayscale, RGB color channels, or alpha transparency.
Any grayscale documents are dithered into black and white before encoding.
Why do some programs fail to open G3 files?
G3 is a highly specialized encoding used mostly inside TIFF containers; standalone .g3 files are less widely supported.
Some G3 files use unusual resolutions or omit headers, making them incompatible with generic image viewers.
Not all software supports both 1D and 2D encoding modes, causing parsing errors.
Why do G3 conversions sometimes fail?
G3 conversions fail when modern tools encounter fax-specific constraints:
Missing Width/Height Information
Raw G3 streams may lack dimension metadata, requiring manual specifications.
Strict Monochrome Requirement
G3 can only accept 1-bit images, so grayscale or color inputs must be converted first.
Non-Standard Fax Encodings
Some fax systems used proprietary modifications to CCITT encoding.
Unexpected Scanline Lengths
Older machines sometimes used non-standard widths, confusing modern decoders.
Raw Compressed Streams
Some .g3 files lack headers entirely, requiring CLI tools like ImageMagick or Faxutils.
Specialized tools handle these variants better than generic image viewers.
Does G3 support metadata?
No-G3 stores only the compressed 1-bit image data.
Fax sender IDs and timestamps were printed on the page itself, not stored in metadata.
TIFF-G3 adds metadata layers, but pure G3 files do not.
What modern uses does G3 still have?
Even today, G3 compression is used in several workflows:
Digital Fax Transmission
FoIP and SIP fax protocols still encode pages using G3 during transmission.
Archiving Legacy Fax Records
Organizations preserve original fax pages for legal or contractual authenticity.
Low-Bandwidth Systems
G3 is ideal for sending black-and-white documents over poor-quality networks.
OCR Training and Benchmarking
G3 documents are used to test OCR performance on low-quality scans.
Unix Fax Software
Tools like HylaFAX, efax, and Ghostscript handle G3 encoding and decoding.
Simple Archival Requirements
G3’s simplicity ensures that documents remain readable long-term.
Telecom Systems
Many telecom providers still maintain nodes that generate or read G3 data.
Document Forensics
Investigators inspect G3 noise patterns to verify authenticity of old faxed pages.
Fax Testing and Simulation
Developers use G3 to simulate fax transmissions for QA environments.
Historical Preservation
Archivists keep G3 documents unchanged to preserve historical accuracy.
Why are G3 files so small?
They store only 1-bit black-and-white data.
Run-length and Huffman-style compression drastically reduce repeated whitespace.
No metadata, color channels, or container overhead are included.
How large can a G3 file get?
Most G3 pages range from 20 KB to 60 KB depending on content.
Densely printed or highly detailed pages produce larger files.
Multi-page archives grow only when several G3 streams are stored together in containers like TIFF.
Does G3 support multi-page documents?
A standalone G3 file contains only one page.
Multi-page handling is implemented through container formats such as TIFF.
Fax machines transmitted pages individually but stored them together externally.
Why do some G3 images appear stretched or squished?
G3 uses non-square pixels, causing distortion if a viewer assumes square pixel geometry.
Incorrect DPI assumptions can alter the displayed proportions.
Raw G3 streams without metadata require manual resolution input.
Is the G3 format still relevant?
Yes-G3 remains a backbone of global fax technology, telecom archives, and enterprise document systems.
Its extremely small size makes it valuable for bandwidth-limited transmissions.
Although modern formats dominate scanning workflows, G3 persists wherever fax compatibility and legacy support matter.
About the G3 Format
G3 is a file format used in specific workflows. The exact characteristics depend on the implementation and chosen settings.
- Format Type
- File format
- Origin
- Industry-developed format
- Common Uses
- Various applications that support G3
- Compression
- Depends on implementation
Sources and References
Format details on this page are based on the official specifications and documentation below.
- Image file type and format guide- MDN Web Docs