TWITTER
Twitter profile picture size: 400 x 400
Twitter post image size: 1024 x 512
Twitter video size: 720 x 720 (square), 1280 x 720 (landscape), 720 x 1280 (portrait)
Twitter ad size (image): 800 x 428
Twitter ad size (video): 720 x 720 (square), 1280 x 720 (landscape), 720 x 1280 (portrait)
LINKEDIN Company pages
LinkedIn company logo size: 300 x 300
LinkedIn cover photo size: 1536 x 768
LinkedIn Sponsored Content image size: 1200 x 627
LinkedIn Hero image size: 1128 x 376
LinkedIn Business Banner image: 646 x 220