SIX to HEIF Converter

Convert DEC terminal images to compact HEIF format online

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Batch Support

Upload multiple SIX images and convert them all to HEIF in one session — no need to repeat the process for each individual file.

Cross-Platform Access

Whether you are on Windows, macOS, Linux, or mobile — SIX to HEIF conversion is available from any connected device.

Retro Graphics Export

SIX encodes images for vintage DEC terminals. Converting to HEIF extracts that artwork into a format modern tools understand.

How to convert SIX to HEIF

1

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

2

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

3

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

About formats

SIX is a file extension for SIXEL (Six Pixel) graphics data, a bitmap graphics format developed by Digital Equipment Corporation (DEC) in 1983 and introduced with the LA50 dot matrix printer. SIXEL encodes images as a sequence of printable ASCII characters, where each character represents a column of six vertical pixels (a 'sixel') — the character's ASCII value minus 63 provides a 6-bit binary pattern, with each bit controlling one pixel in the vertical column. The encoding is structured as a series of sixel bands (each six pixels tall) across the image width, with control sequences for color selection (up to 256 registers with HLS or RGB specification), repeat counts (run-length encoding for efficiency), carriage return, and newline commands. SIXEL data is transmitted to the output device using DEC's standard escape sequence protocol, embedded within the text stream alongside regular character output. Originally designed for DEC's line of printers and later supported by DEC VT-series terminals (VT240, VT330, VT340), SIXEL has experienced a remarkable revival in modern terminal emulator software. One advantage is terminal-native image display: SIXEL allows images to be rendered directly within a text terminal session without requiring a graphical window system, enabling command-line tools to display graphs, photographs, and previews inline with text output. This capability has driven adoption in modern terminals like mlterm, xterm, WezTerm, and foot. SIX/SIXEL data can be generated by ImageMagick, libsixel, and chafa, and viewed in any SIXEL-capable terminal emulator.
Initial release: 1983
HEIF (High Efficiency Image File Format) is a container format for images and image sequences standardized by the Moving Picture Experts Group as ISO/IEC 23008-12, first published in 2015. HEIF is built on the ISO Base Media File Format (ISOBMFF, the same container used for MP4 video), providing a flexible structure that can hold single images, image collections, image sequences (like animations or bursts), and derived images with non-destructive editing operations. The container is codec-agnostic — while the most common implementation pairs HEIF with HEVC/H.265 compression (branded as HEIC by Apple), the standard also accommodates AV1 compression (creating the AVIF variant), H.266/VVC, and other future codecs. HEIF supports features that JPEG lacks: 10-bit and 12-bit color depth, wide color gamuts (Display P3, BT.2020), lossless compression, alpha transparency, depth maps, thumbnail images, and Exif/XMP metadata — all within a single file. Auxiliary image items can store computational photography data like depth maps, HDR gain maps, and semantic segmentation masks. One advantage is the format's future-proof architecture: by separating the container from the codec, HEIF can adopt newer, more efficient compression technologies without changing the file structure, metadata handling, or application-level APIs. The substantial compression improvement over JPEG is another core strength — HEVC-based HEIF typically achieves 40-50% file size reduction compared to JPEG at the same visual quality, beneficial for storage and bandwidth. HEIF is supported by Apple's ecosystem (iOS, macOS), Windows 10/11, Android 10+, GIMP, ImageMagick, and Adobe products.
Initial release: 2015

Frequently Asked Questions

Why convert SIX to HEIF?

SIX encodes images as text for DEC terminals — useless outside that environment. Converting to HEIF yields a standard image you can use anywhere.

What programs can open HEIF?

Apple Photos, Windows Photos (with codec), Adobe Lightroom, Photoshop, GIMP, and most modern mobile gallery apps support HEIF.

Can I use this converter on any operating system?

The tool is browser-based and works on Windows, macOS, Linux, ChromeOS, and mobile platforms — no OS-specific software needed.

Is SIX to HEIF conversion fast?

The process is fast — cloud-based processing handles SIX to HEIF conversion in seconds for standard-sized images, even on slower connections.

Does Convertio support batch SIX to HEIF conversion?

Batch conversion is supported. Queue as many SIX files as you need and convert them all to HEIF in a single run — no repeating steps manually.