It’s not possible to copy and paste an image into a blog, and write alt text for that image. To add alt text to an image you have to either:
- Upload the image to an external image hosting site, make the tag in HTML and add alt text, putting that into your blog
- Upload the image to an external image hosting site, and add it via markdown with alt text.
- Upload an image to a blog post (draft blog post), preview that draft blog post, copy image location, paste it into your blog post with either HTML / Markdown and write the alt text that way
What I think would work nicely:
When you click an image you’ve uploaded, you get this nice box:
It would be nice to see an “alt-text” button that letts you write alt text for the image
See also this post on automatically adding alt text: