What a post URL looks like
Open the post in a browser. The address includes the blog name and a post id, on tumblr.com or on a custom blog domain that still serves that post. Copy that address. The blog homepage, a tagged page, and a search page are lists of posts, not one file.
Dashboard links that only work while you are logged in will fail here. The post has to be visible on the public web. Private blogs and password blogs are not opened, and this page never asks for a Tumblr password.
Sets, GIFs, and videos hosted on Tumblr
A photo set comes back as one image per frame, in the order the post shows them. You can save a single frame. GIFs stay in the format Tumblr serves, which is often a GIF and sometimes a short silent video. Native video posts return that video.
Many posts only embed another site. A YouTube player, a Spotify card, or a quoted tweet is not a Tumblr file. Those need the original link on the matching downloader, if one exists, or they are simply not downloadable from the Tumblr page. Text posts with no media return nothing.
Size and reblogs
You get the file the public post exposes, not a blown-up thumbnail from the dashboard. Older posts are sometimes only available in a smaller size because that is what was uploaded. We do not sharpen them.
A reblog can show the original media or only a link back to it. If the reblog page does not include the file, open the original post and paste that URL instead. Captions and tags are not saved as a separate document.
How to save one Tumblr post
Step 1
Copy the post address
Open the single post and copy the browser URL. Include the blog name and the post id. Do not copy the blog root.
Step 2
Paste it above
Press Download. Photo sets list one image per frame. A native video lists the video. Embeds from other sites are not unpacked.
Step 3
Save each file you need
Preview the frame or the video, then save it. GIFs remain the file Tumblr served.
Photo sets, GIFs, and native video
Images and GIFs
Photo posts and GIFs, one frame at a time in a set.
Native video
Video uploaded to Tumblr, when the public post includes the file.
Not embeds
YouTube, Spotify, and other players inside a post are not Tumblr files.
Blogs, embeds, and original size
Can I download a whole blog?
No. Paste one post link at a time.
Why did a video post fail?
The post is probably an embed from another site, or the blog is private. Open the original file's own link.
Do dashboard-only posts work?
No. The post has to be public on the web, without a Tumblr login.
Is the original size kept?
You get the file the public post exposes, not an enlarged thumbnail.