How to Minimize a YouTube Player for Tumblrby Andrea Ruiz
When you create a Tumblr video post, you can quickly embed any YouTube video that allows embedding by pasting the video's URL into the "Embed" field. Embedding enables your followers to stream the videos from your post on their dashboards, but it also embeds the video according to your layout's default video-embedding size specifications, which may resize your video to be quite large at a low resolution. If you want to customize the size of the YouTube Player to a smaller size than your theme's default, you must paste customized embed code directly into the HTML code of an individual post.
Customizing Player Size
Visit the YouTube video you want to embed in your post, and click the "Share" tab in the video menu.
Select the "Embed" tab in the Share menu, and then select "Custom Size" from the drop-down menu.
Enter the custom pixel width and height at which you want your YouTube player to display in your blog post. YouTube automatically resizes the height and width to maintain the aspect ratio of the embedded player.
Copy the entire embed code to your computer's clipboard.
Embedding Custom YouTubes on Tumblr
Select the blog to which you want to post the YouTube player from the drop-down list of blogs on your dashboard, if your account has more than one blog.
Click the "TEXT" button to create a new text post on your blog.
Add any text you want your post to have, including tags and a subject line, and then click the "<HTML>" button in the post-editing form to switch to HTML view.
Paste the YouTube embed code where you want the player to display in the post.
Click the down arrow in the "Post" button and select "Preview On Your Blog" to check that the player displays as the size you'd like in your Tumblr layout, and then click the "Post" button to publish the post on your blog.