Free Lossless Image Format

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Free Lossless Image Format
FLIF logo
FLIF encoder.png
Filename extension.flif
Internet media typeimage/flif
Uniform Type Identifier (UTI)public.flif
Magic numberFLIF
Initial release3 October 2015; 4 years ago (2015-10-03)[1]
Latest release
(28 April 2017; 2 years ago (2017-04-28)[2])
Open format?Yes

Free Lossless Image Format (FLIF) is a lossless image format (current version FLIF16 specification) claiming to outperform PNG, lossless WebP, lossless BPG and lossless JPEG 2000 in terms of compression ratio on a variety of inputs.[3]

FLIF supports a form of progressive interlacing (a generalization of the Adam7 algorithm) with which any partial download of an image file can be used as a lossy encoding of the entire image.


The format was initially announced publicly in September 2015,[4] with the first alpha release occurring about a month later, in October 2015.[1]

The first stable version of FLIF was released in September 2016.[5]


For compression, FLIF uses MANIAC (Meta-Adaptive Near-zero Integer Arithmetic Coding), a variant of CABAC where the contexts are nodes of decision trees which are dynamically learned at encode time.

FLIF uses the reversible YCoCg color space[6] (unlike Y′CBCR that loses some color information to rounding errors, independently of its use in otherwise lossy JPEG). Not yet implemented are some features,[7] e.g. other "color spaces (CMYK, YCbCr, ...)". The color space conversion is faster, but the overall decoding (and encoding) is still slower than it needs to be, or some of the competition, even with the better color space as that is only a small fraction of the overall process. The format supports an optional alpha channel (RGBA) like PNG (but unlike JPEG); and progressive coding, similar to PNG (unlike it, progressive compression doesn't increase file-size), but as FLIF's algorithm is more complex (and partly, may not have had as much tuning of the implementation yet), it has a higher computational cost; at least lower bandwidth requirements can offset some of that extra time. Progressive coding reduces FLIF's performance.

FLIF supports grayscale, RGB and RGBA with color depth of 1 to 16 bits per channel.[6]

FLIF has some parameters, and can result in differently sized images, with tuning, or done by flifcrush tool. All of those images are still lossless. FLYF (for lossY), is also considered, and that would be the file-ending; while both could describe either and ending just used to indicate.[incomprehensible]


XnView supports FLIF since version 2.36.[8]

ExifTool supports reading and writing metadata in FLIF images since version 10.31.[9]

UGUI-FLIF supports preview and converting PNG file to FLIF.[10]

IrfanView supports reading FLIF images since version 4.52.[11][12]


  1. ^ a b "Release v0.1-alpha". FLIF-hub/FLIF. 3 October 2015.
  2. ^ "Release v0.3". FLIF-hub/FLIF. 7 June 2017.
  3. ^ "FLIF is a New Free Lossless Image Format That Raises the Compression Bar". PetaPixel. 2 October 2015. Retrieved 20 October 2016.
  4. ^ "Free Lossless Image Format (FLIF)". 6 September 2015. Archived from the original on 12 September 2015.
  5. ^ "Release v0.2". FLIF-hub/FLIF. 22 September 2016.
  6. ^ a b "FLIF16 Specification". Retrieved 28 November 2019.
  7. ^
  8. ^ Pierre-Emmanuel Gougelet (8 November 2016). "XnView 2.39". XnView. Retrieved 15 September 2017.
  9. ^ Phil Harvey (19 October 2016). "ExifTool Ancient History". ExifTool. Retrieved 1 November 2017.
  10. ^ "UGUI: FLIF Download". Retrieved 27 December 2018.
  11. ^ Irfan Skiljan (12 December 2018). "History of IrfanView Changes/Versions: [4.52 current 2018-12-12]". Retrieved 28 December 2018.
  12. ^ Kuki Dent (13 December 2018). "IrfanView 4.52 has been released today -IrfanView Support Forum". Retrieved 28 December 2018.

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