Misskey用 メディア一括ダウンローダー(非公式) by nyyn_dev

Features:
- Just enter an instance hostname and username to fetch image, video, and audio attachments from that account's posts
- Choose which file types to download: image, video, audio, or other
- Filter posts by a custom date range
- Optionally include or exclude attachments from renotes
- Toolbar icon shows live download progress, with a desktop notification when finished
- Customize the save folder name and filename pattern from the Options page
- Set the filename style (auto-numbered or original) independently for each file type (image / video / audio / other)
- Automatically sort downloads into per-type subfolders (images / videos / audios / others), with an option to turn this off
- Choose how numbering works when a single post mixes multiple file types: number only the downloaded files, or number them by their original position in the post
- Optionally convert webp images to PNG or JPG on save (animated webp is detected automatically and left unconverted)
- Optionally show a native "Save As" dialog for each file if you'd rather pick the destination manually

How to use:
1. Click the toolbar icon to open the popup
2. Enter the instance hostname (e.g. misskey.io) and the username
3. Set the file types, an optional date range, and any other options, then click "Start"

Privacy:
The instance hostname and username you enter are only used to communicate with that instance's public API. No data is ever sent to any third-party server, and downloaded media is saved locally to your own device only.