Skip to content


Subversion checkout URL

You can clone with
Download ZIP
Convert all CSS background images to DataURI and MHTML.
Pull request Compare This branch is 6 commits behind josephj:master.
Fetching latest commit...
Cannot retrieve the latest commit at this time.
Failed to load latest commit information.


dataurize, Tool Replacing CSS Background Images to Data URI and MTHML

Using Data URI instead of binary images is a very good idea in web development. One binary image means an extra HTTP request in your request. It's easy to have 30+ images on a single page, which means you have 30+ HTTP requests. The more requests means the poor performance of your website.

A common solution to this is CSS Sprites, combining multiple images into one. However, the maintenance cost of choosing this apporach is really expensive. You always have to use some softwares like Photoshop or Fireworks to maintain. And carefully using CSS attributes like background-position, overflow: hidden, width, and height to make it work. A engineering industry shouldn't have such ridiculous development process.

Data URI transforms image to Base64 encodeed string. That means you can have a image without any HTTP Request. Though the file size blows to 2 to 3 times larger, Gzip makes it worthy of the investment. And remember request is expensive than file size in most of situations.

The only thing we need to take care is browser compatibility issues. Internet Explorer version before 8 doesn't support Data URI. However, something similar called MHTML make it up.

dataurize is a simple PHP script converting your tranditional CSS file to the one using Data URI and MHTML. You don't have to worry about browser compatibility because it also attaches equivalent MHTML into your target CSS.


You can try dataurize Web Interface to convert a CSS file of your website.


  • ImageMagick 6.3.7+
  • PHP 5.2.6+


$ git clone git:// ~/dataurize
$ sudo mv ~/dataurize/dataurize /usr/bin/
$ sudo chmod +x /usr/bin/dataurize


Usage: dataurize <input> <base> [options]

    --output=<output>    Assign an output file. By default it overwrites your original file.
    --print              Print output directly instead of generating or overwriting a file.
                         By default, this option is disabled.
    --separate=<output>  Separate MHTML to a single file. By default, this option is disabled.
    --no-mhtml           Don't enable MHTML. Use this option if you don't want to use MHTML for legend IE.
                         It however doesn't hurt browser compatibility by adding *background-image(<Original Image Path>).
                         By default, this option is disabled.
    --size-limit=<bytes> It might still damage website performance if you transform an image with large file size.
                         The default file size is 1024 bytes.
    --help               Show this help.

Sample: ./dataurize foo.css --output=foo2.css


Currently all CSS files in are dataurized by this script before deployment. Our best practice is not converting images which is larger than 5 KB. Or it causes CSS file size becomes too large to be affordable.

$ dataurize <input> <base> --size-limit=5120

Known Issue


Something went wrong with that request. Please try again.