A developer building an ambigram generator on WordPress reports that HTML5 canvas content displays correctly on screen but exports as a blank image when using canvas.toDataURL(). The code draws text using a custom font, yet the downloaded PNG file is completely white, suggesting a rendering or timing issue during the export process.

The likely culprit is web fonts not fully loading before the canvas is drawn. Browsers may render the text visually but fail to capture it in the canvas bitmap if the font resource isn't ready. This is a common pitfall when exporting canvas elements, especially with custom or asynchronously loaded fonts.

To fix this, ensure fonts are fully loaded using the FontFaceSet API or a `document.fonts.ready` promise before executing draw commands. Verify the canvas's intrinsic dimensions match its displayed size to avoid scaling artifacts. Testing the export after a deliberate delay can confirm if timing is the root cause.