How to embed base64 images in HTML (Tutorial)

When creating HTML files you can include images by several means using local images, external URLs, and by embedding image as base64 content. This tutorial covers how base64 images can be included and why you would want to.

Why should I embed images as base64?

Embedding images as base64 content will decrease the number of requests required as the images are now part of the HTML file. However, the base64 content will be between 20-25% larger than the image. This means that this approach will be beneficial for small to medium images but large images would have a much larger impact on performance.

How to embed base64 images in HTML

1. Convert image to base64 string. There are lots of ways to do this (Java example below).
2. Create an img tag with an empty src value
3. Construct a data URI in the src attribute
• Add a data media type to match the original image
• Add a charset that matches that used in the encoding
• Add the base64 data you created previously

Here is Java code to create base64 image data…

final ByteArrayOutputStream os = new ByteArrayOutputStream();

try {

    //Can be any support image format

    final String formatName = "jpg";


    //Convert image data to Base64 and write date to the output stream

    final BufferedImage image = ImageIO.read(new File("/path/to/file"));

    ImageIO.write(image, formatName, Base64.getEncoder().wrap(os));


    //Create Base64 string

    final String base64 = os.toString(StandardCharsets.UTF_8.name());


} catch (final IOException ioe) {

    throw new UncheckedIOException(ioe);

}

Add this to your HTML…

<img src="data:image/jpeg;charset=utf-8;base64,<DATA>" alt="Description of the image" />

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