LeptonGUI: Dropbox Lepton image format converter

Martin Brinkmann
Nov 28, 2016
Updated • Nov 29, 2016

LeptonGUI is a free program for Windows devices to convert images to and from Dropbox's Lepton image format without having to use the command line to do so.

Dropbox released Lepton, an image compression format, in the middle of 2016. The new format achieves 22% better compression of JPEG images without quality loss according to Dropbox.

The company uses Lepton on its servers to save storage space. According to the announcement, it encoded 16 billion images already when it made the announcement which saved "multiple petabytes of space".

Dropbox released Lepton's source code and a command line version for Windows. It can be downloaded from GitHub but only run from the command line.


LeptonGUI adds a graphical user interface. It is limited in comparison to the command line version as it does not support changing conversion parameters.

The program is portable, and all you have to do to get started is to run it after you have downloaded it and extracted the archive it is provided in.

Use the "import files" button to load one or multiple jpeg or Lepton images. The current version appears to have a bug right now that blocks information about processed images that you have dragged and dropped into the interface from being listed by LeptonGUI.

The images are converted just fine, but you won't see that reflected in the interface.

All images are listed with their name and extension, path on the local system, and original size in bytes. Note that you can load unsupported image formats such as png. Those won't be converted to the Lepton (.lep) format when you click on convert all in the interface.

A click on the button converts all jpg images to lep format. The original images are kept, and a new .lep format image is saved to the same directory in the process.

LeptonGUI highlights the saving in the status bar after the process. You will also see how much the conversion saved by looking at the "saving" column which highlights that for any processed image individually.

Closing Words

LeptonGUI makes it easy to convert any number of supported images to Dropbox's Lepton format, or from the format.

The only reason to do so right now is that it requires less storage. I'm not aware of viewers that support the .lep format right now, which means that the format is not suitable right now if you need to view images.

There is probably an obscure image viewer around that supports the format, but the major ones don't seem to support it yet.

The command line version supports additional options that advanced users may find useful so that they prefer to use that version instead. Options include setting allowing the conversion of progressive jpg images, or setting memory and thread memory to custom values.

The command line version of Lepton ships with LeptonGUI. You can download the package from Download Crew.

LeptonGUI: convert images to Dropbox's Lepton format
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LeptonGUI: convert images to Dropbox's Lepton format
LeptonGUI is a free program for Windows devices to convert images to and from Dropbox's Lepton image format without having to use the command line to do so.
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  1. Randy Vogel said on November 29, 2016 at 9:20 am

    Lessee, my wife has a thing about shooting pictures to the tune of > 50 GB/mo
    22% compression sounds great if the compress/inflate process could be initiated on the fly (by the viewer apps, for example).
    Or even for offline home storage & cloud backups…
    Thanks for the tip!

  2. dwarf_t0ssnn said on November 29, 2016 at 2:14 am

    Still a better name than “Shumway”, but juuuust barely. That out of the way, this looks amazing for those with *vast* websites which host tons of JPGs. File compression is just neat in general.

  3. RossN said on November 28, 2016 at 11:29 pm

    Found it here. Tested. Works OK.

  4. fena said on November 28, 2016 at 11:26 pm

    Interesting article but finding the link is a challenge.

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