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While developing a new JS framework at my workplace (unfortunately non open source), I'm using Node.js to handle all dependencies (thanks to npm) and the build process (thanks to jake). The other day we have decided to write a simple jake task which gives us the ability to include Base64 encoded images into CSS files on build.

The biggest advantage of this technique is that you could have only one CSS file with all your images included. There are few disadvantages as well, the CSS file could be much bigger and indeed you can't cache your image files separately anymore, but you can cache the CSS file instead, so it won't be a problem. Not decided yet which will be the default option in future releases, but at least we have the option to embed images. :)

Please find this tiny function below (copied from the build script):

var fs = require('fs');
var path = require('path');

function cssIncImages(cssFile) {
    var imgRegex = /url\s?\(['"]?(.*?)(?=['"]?\))/gi;
    var css = fs.readFileSync(cssFile, 'utf-8');
    while (match = imgRegex.exec(css)) {
        var imgPath = path.join(path.dirname(cssFile), match[1]);
        try {
            var img = fs.readFileSync(imgPath, 'base64');
            var ext = imgPath.substr(imgPath.lastIndexOf('.') + 1);
            css = css.replace(match[1], 'data:image/' + ext + ';base64,' + img);
        } catch (err) {
            console.log('Image not found (%s).', imgPath);
    // fs.writeFileSync(cssFile, css, 'utf-8'); // you can overwrite the original file with this line
    return css;
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Kalman Speier



Kalman Speier

Logbook of my journey in software development.

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