# How do figure out the endianness of a JPG? **URL:** \ **Category:** Factual Questions\ **Created:** [October 4, 2004, 11:45pm UTC](https://boards.straightdope.com/t/how-do-figure-out-the-endianness-of-a-jpg/267570 "2004-10-04T23:45:07Z")\ **Posts on this page:** 7\ **Page:** 1
**Author:** ![jawdirk](https://avatars.discourse-cdn.com/v4/letter/j/df705f/32.png) [@jawdirk](https://boards.straightdope.com/u/jawdirk)\ **Post date:** [October 4, 2004, 11:45pm UTC](https://boards.straightdope.com/t/how-do-figure-out-the-endianness-of-a-jpg/267570/1 "2004-10-04T23:45:07Z")
Is there an easy method, using a Hex-editor, say, to discover the endianness of a JPG? Thanks. ---
**Author:** ![AHunter3](https://sea3.discourse-cdn.com/straightdope/user_avatar/boards.straightdope.com/ahunter3/32/368_2.png) [@AHunter3](https://boards.straightdope.com/u/AHunter3)\ **Post date:** [October 5, 2004, 2:40am UTC](https://boards.straightdope.com/t/how-do-figure-out-the-endianness-of-a-jpg/267570/2 "2004-10-05T02:40:15Z")
Didn’t know it varied. I’ve never had a graphic program offer me the option, or something likely to be its equivalent (i.e., “Windows byte-order” versus “Mac byte-order” or something akin to that). What would cause a JPEG to be little-endianned as opposed to big-endianned in the first place? Or are you asking, not for “a given JPEG”, but rather “for all JPEGs in general”, i.e., “what’s the standard byte-order of these puppies”? ---
**Author:** ![Bytegeist](https://avatars.discourse-cdn.com/v4/letter/b/9dc877/32.png) [@Bytegeist](https://boards.straightdope.com/u/Bytegeist)\ **Post date:** [October 5, 2004, 3:10am UTC](https://boards.straightdope.com/t/how-do-figure-out-the-endianness-of-a-jpg/267570/3 "2004-10-05T03:10:33Z")
According to [this guy](http://www.cs.umass.edu/~verts/cs32/endian.html), as well as several other pages covering the format, the integer fields inside a JPEG file are all big-endian. (The most significant bytes precede the less significant ones). ---
**Author:** ![Muffin](https://sea3.discourse-cdn.com/straightdope/user_avatar/boards.straightdope.com/muffin/32/4341_2.png) [@Muffin](https://boards.straightdope.com/u/Muffin)\ **Post date:** [October 5, 2004, 3:44am UTC](https://boards.straightdope.com/t/how-do-figure-out-the-endianness-of-a-jpg/267570/4 "2004-10-05T03:44:04Z")
Status or non-status? ---
**Author:** ![astro](https://avatars.discourse-cdn.com/v4/letter/a/9dc877/32.png) [@astro](https://boards.straightdope.com/u/astro)\ **Post date:** [October 5, 2004, 10:19am UTC](https://boards.straightdope.com/t/how-do-figure-out-the-endianness-of-a-jpg/267570/5 "2004-10-05T10:19:39Z")
[A Sample JPEG Image File Data structure.](http://www.geocities.com/tapsemi/datastruct.html) [JPEG / JFIF image file format](http://www.geocities.com/marcoschmidt.geo/jpeg-image-file-format.html) > [@](#): > > File structure > A JPEG bitstream is a sequence of data chunks, each chunk starts with a marker value. A marker is a 16 bit integer value, **stored in big endian byte order** , with the most significant byte set to 0xff. The lower byte of the marker value determines its type. A marker is followed by a 16 bit integer value for the size. ---
**Author:** ![Polycarp](https://avatars.discourse-cdn.com/v4/letter/p/82dd89/32.png) [@Polycarp](https://boards.straightdope.com/u/Polycarp)\ **Post date:** [October 5, 2004, 1:56pm UTC](https://boards.straightdope.com/t/how-do-figure-out-the-endianness-of-a-jpg/267570/6 "2004-10-05T13:56:47Z")
So a corrupted JPEG file could be referred to as Blefuscated? 😛 ---
**Author:** ![jawdirk](https://avatars.discourse-cdn.com/v4/letter/j/df705f/32.png) [@jawdirk](https://boards.straightdope.com/u/jawdirk)\ **Post date:** [October 5, 2004, 5:43pm UTC](https://boards.straightdope.com/t/how-do-figure-out-the-endianness-of-a-jpg/267570/7 "2004-10-05T17:43:40Z")
Thanks for all your answers. That is very helpful. Andrew