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Adding a Base64-encoded SVG image as a WordPress admin menu icon

For our new plugin Kanban, we have a custom WordPress admin menu page. So of course I wanted to add a custom icon to it.

I looked a the Yoast SEO WordPress plugin which has a custom plugin, and discovered it wasn’t an image,but a Base 64 encoded svg image.



Great! I’d rather do that than deal with an image.

But frustratingly, you can find a lot about the WordPress dashicons as a font, but there’s not a lot written about using a Base 64 encoded svg image. On the add_menu_page WordPress documentation, there’s a reference to it, but not how to use it, or how big the image should be.

Screenshot at Sep 17 18-37-32


I finally wound up using the source from Yoast to find how they did it in their plugin.

Screenshot at Sep 17 18-35-34


The last problem was figuring out how big the image should be. Googling around, I found one article, and at the very bottom it said the icon should be 20 x 20.

So I created an image in Photoshop, and then used http://b64.io (or https://www.base64-image.de, I don’t remember) to convert my image to a Base 64 string, and dropped that into my code.

It turns out that 20px x 20px is too big, but it’s close. I wound up cropping it down to 19px x 17px, with an extra couple pixels on the left to center it. I think it turned out well!

Screenshot at Sep 17 18-43-43

So to summarize:

  1. Make your image around 18px x 18px
  2. Use http://b64.io or https://www.base64-image.de to get your image as a Base 64 encoded string.
  3. Add it to your code:
    // Base 64 encoded SVG image.
    $icon_svg = 'data:image/png;base64,iVBORw0...'; // base 64 string goes here