Alt texts
So called alt-texts (alternative text) are the default means to make visual content accessible in a descriptive format. But using them correctly is not an easy, and for sure not precise, science.
For a first deep dive, this text aims to summarize all the most important aspects:
Alt-texts: The Ultimate Guide
Decision trees
Decision trees are intended to help decide whether and what kind of alt text to use.
WAI Web Accessibility Tutorials: An alt Decision Tree
Top 5 Questions Asked in Accessibility Trainings
Content design considerations
Writing alt texts is not an easy task, but a key part of the design process. Creating good text descriptions for images is an art of its own, but not one that couldn't be acquired.
Writing great alt text: Emotion matters
The case for describing race in alternative text attributes
In this article, Tolu Adegbite makes the case for describing race (and gender, where possible) in image alt texts.
Also the appropriate length of an alt text is a debated aspect:
Just How Long Should Alt Text Be?
Making SVGs accessible
Things work slightly differently if SVG vector graphics are embedded directly (not as an <img>).
Accessible SVGs: Perfect Patterns For Screen Reader Users
AI to the rescue?
Recently, one may occasionally see suggestions to use AI technology to compensate for a lack of alt texts, or to simply make writing them obsolete.
Microsoft Edge now provides auto-generated image labels
This is a heavily disputed approach; the debate is (along with, for example, environmental concerns, given the energy consumption of AI) largely unfolding around the question whether using AI to interpret images without alt text should rather be left to the user, than generating texts that have not been gone through editorial review.
Alt texts in HTML email
The same rules apply for HTML used in email as well. With their generic browsing engines, there are however a long range of aspects to be considered.
The Ultimate Guide to Styled ALT Text in Email
A comprehensive resource (note: from 2016; some of this may be outdated) on alt texts in HTML email this guide provides practical information on how to use alt texts in email, and technical limitations by some email clients' quirks.