McSib said:
Hello, as I am developing a downloader that sends requests to e621's API, I would like to know if there are any changes that may happen to the API when this leaves beta? I want to make sure that my program is okay as it is right now, or if I need to start developing changes for when this releases.

As far as I'm aware there's changes to the JSON data returned, XML probably won't be supported, and when updating posts only the changed tags should be returned, such as:
canine -feline

And although not implimented yet, I'm pretty sure the endpoints are planned to be changed to a dedicated /api/ path, rather than appending .json to the URL.

Here's an api page for a post, so you can see the data that's currently returned:
https://beta.e621.net/posts/190.json

Overall it's probably best to wait till the api's more finished to develop for the new/beta site, as things are likely to change a bit.