I have seen a lot of the time on YouTube that people are using images which are copyrighted or may be copyrighted in their YouTube video thumbnails.
My question is: is it allowed to use copyrighted images in YouTube video thumbnails?
Here is an example in which pewdiepie, a famous youtuber, uses an image of Leonardo de Caprio in his video thumbnail.
And here is the link of the original picture: http://www.telegraph.co.uk/film/the-revenant/leonardo-dicaprio-golden-globes-win-oscars/
Best Answer
When you use content (picture or a photo or a sound or even a small article) in your website or in your Social Media page and this content is taken by you from another website, you should first search for copyright clarifications on the "Terms and Conditions" page of the source website or News Portal.
For example in http://www.telegraph.co.uk/film/the-revenant/leonardo-dicaprio-golden-globes-win-oscars/ , go to the Terms & Conditions subpage of Telegraph's news portal and read the 6th paragraph:
Now in case a News Portal does not have a "Terms and Conditions" subpage it does not mean that you can reproduce their content without their permission.
Another possibility is that some webpages or News Portals or Blogs they also reproduce content from other News Portal without their permission, so do not get in this loop because you will be considered equally a violator of the source's copyright terms.
If possible, always ask for permission from the source website or News Portal before reproducing their content.