If you have an iPhone 6s or 6s Plus, you can post Live Photos to your Tumblr. Create a photo post with a Live Photo just like you’d create a still photo post, and tiny concentric circles in the corner of the Live Photo will show others that it’s interactive.
Other folks with an Apple device running iOS 9.1 or above can tap and hold the photo to see a three-second clip with sound. If someone is viewing your post on a browser, an older iOS version, or different device, it will appear as a still photo without sound.
Note that if you’re not connected to wifi, you’ll need to tap on a Live Photo to download it, then you can tap and hold to view. This helps avoid too much data usage.