I'll add that if you don't want to put additional info for the fic/chapter in the end notes (maybe the chapter ends on a cliffhanger or a banger of a line and you don't want to risk a reader accidentally seeing it while reading end notes) and would prefer to have it in the beginning notes in a way that won't spoiler/upset people who don't want, there's a way to do that!
In the beginning notes, type <details>. Everything that comes after this and before the details end tag (</details>) will be hidden behind a dropdown, which will be represented by a little triangle upon publishing. A reader clicks (or taps on mobile) the little triangle, and the information is revealed. It'll look like this:
When the triangle is clicked, it will go from pointing at "Details" to pointing downwards, and the content hidden inside the details will unfold under "Details."
If you'd like to give specifics about what's inside the details tag, you can do that using the summary tag. Right after <details>, type <summary>. Write whatever description you want (HTML tags like bold, italics, etc. can be used here), end the description with </summary>, then proceed to write the information you want in the details tag. Now, when the chapter/fic is published, your summary will replace "Details" next to the triangle. Here's an example from one of my own works, where I've used bold, small, and italic HTML tags to further format my summary:
In practice, the backend of HTML in the beginning notes looks like this:
<details><summary><strong>Regarding the "Additional Warnings In Author's Note" Tag</strong> <small><em>(contains some spoilers for the story)</em></small></summary>
[additional warnings]</details>
For more information about the details tag and to play around with it some outside of AO3, I recommend checking out the W3 Schools page on the tag.
You can also use the details tag (and accompanying summary tag) in the summary of a work or series, as well as the Notes section on a summary. Or in comments. On info pages for Collections. In your AO3 profile. The sky's the limit!*
* The sky is not in fact the limit. Pretty sure this won't work in the title field of a work, and it definitely won't work in any of the tag fields.
snowghoul
jbbartram-illu
theartofmadeline
dailybridgerton
areudirty
turnnoffyourmind
stormborns
