Social Media Dimensions (as of 8/1/2018)

Yo
Tracking down dimensions for social media post across 20 different forums and websites can be tedious - so here's a guide with some helpful templates. Unfortunately, these will likely be irrelevant in another month when one of these sites is sure to make changes :)
If you'd like to skip this pretty formatting and head straight to a sweet spreadsheet by Sprout Social, click here!
And if you're just here for Adobe Illustrator and Photoshop Templates, click here!
Facebook DIMENSIONS
Profile Image
Optimal Size: 180 x 180 pixels
Cover Photo
Optimal Size: 851 x 315 pixels
Post Images
Optimal Size: 1,200 x 630 pixels
Shared Link Images
Optimal Size: 1,200 x 627 pixels
General Note: Filetype should be .jpg. If you upload something that is bigger than the optimal size, it will be resized to fit.
Instagram DIMENSIONS
Profile Image
Size: 110 x 110 pixels (but it will crop the image as a circle--watch your corners!)
Photos
Square: 1080 x 1080 pixels
Vertical: 1080 x 1350 pixels*
Horizontal: 1080 x 566 pixels*
*Note that when you upload an image that is not square, the thumbnail will still crop to a square.
Twitter DIMENSIONS
Profile Photo
Size: 400 x 400 pixels
Header Photo
Size: 1500 x 500 pixels
In-Stream Photo
Size: 506 x 253 pixels
Youtube DIMENSIONS
Profile Photo
Size: 800x800 pixels
Videos
Most common sizes: 1920x1080 or 1280x720
Video Thumbnails
Size: 1280x720
Channel Cover
This one is tricky, bear with me:
Full size cover is 2560x1440
For viewing on a computer monitor, the size is 2560x423
For viewing on Tablet, the size is 1855x423
For viewing on any device, the size is 1546x423
So here's what that means. Upload an image that is 2560x1440, but fit all the important information within 1546x423. See the image example below:

Twitch DIMENSIONS
Profile Photo
Size: 800x800 pixels
Profile Banner
Size: 1920x480 pixels
Video Player Banner
Size: 1920x1080 pixels
Video Thumbnail
Size: 1280x720 pixels
Cover Image
Size: 1200x380 pixels
Info Panels
Size: 200x320 pixels
Links: