I am currently working application that uses e621's API, and I am trying to fetch a post's comments, but the API Documentation does not state how to fetch comments. I've tried using https://e621.net/comments.json but that does not return comments but seemingly random posts. I've also tried https://e621.net/posts/[post_id]/comments.json and that returns a piece of html, which is the comment section of the post, but it doesn't seem like that is supposed to happen. Does anyone know how to do it properly?

I believe the proper way to fetch a post's comments is to send a GET request to https://e621.net/comments.json?group_by=comment&search[post_id]=(post's id)

For example, you can get the comments of post #3000000 by sending a GET request to https://e621.net/comments.json?group_by=comment&search[post_id]=3000000

There are also limit and page parameters that control the number of fetched comments and the page of the comment's list respectively.

Donovan's unofficial API documentation has a good bit of info about comments (and some other endpoints that aren't mentioned in the official docs) which is worth checking out.

kora_viridian said:
That is weird. That might be worth a post in the bug report thread.

It looks like the HTML is wrapped in JSON, and then there's also a list of posts in the JSON after that, but I'm not sure how it selects the posts for that list.

It isn't a bug, it's very much intentional. The default group_by is post, which starts its relation at posts, with comments being pulled in on the visual side. This is utterly useless for api usage, as you've seen.