Choosing [the] least CO2-emitting form of digital communication

The text format used impacts the weight of text. Done properly, HTML is a light, environmentally friendly way to publish text. 1,000 words of text optimally formatted in HTML should weigh no more than 7 KB. However, if you simply save a thousand words as HTML using Microsoft Word, for example, that file will likely be more than 50 KB because Word introduces lots of unnecessary code. 1,000 words as a Word document will be about 16 KB. Saving 1,000 words as a PDF will be more than 60 KB. So, for the exact same piece of text, PDF can be nine times more polluting than optimized HTML. For this and many other reasons, optimized HTML should be the choice of the environmentally conscious communicator and designer.

It is a good thing to have one more reason for publishing html online rather than pdf or docx. And yet we still see interactive PDFs, possibly the single worst ‘web’ format ever invented.