By default, you can upload videos that are up to 15 minutes long. To upload longer videos, verify your account with the following steps.
1. On a computer, visit the upload page at www.youtube.com/my_videos_upload
2. Click Increase your limit at the bottom of the page, or visit https://www.youtube.com/verify
3. Follow the steps to verify your account with a phone. You can choose between receiving the verification code through a text message (on a mobile phone) or an automated voice call.
Make sure you’re using an up-to-date version of your browser so you can upload files greater than 20GB. The maximum file size you’ll be able to upload to YouTube is 128GB and the maximum duration is 11 hours.
I uploaded a long video before verifying my account.
If you forgot to verify your account before uploading your long video, you’ll be prompted to do so after your video has finished processing. You may also see a “Rejected (length of video too long)” error in your Video Manager. (Here, click Verify account button next to the video.)
Once you’ve verified your account, click Activate this video in your Video Manager to publish it. Activated videos are automatically set as private videos, so make sure to check the privacy settings for your video and edit them if you’d like.
I can’t find the “Increase your limit” link.
If you can’t find the link described above, it’s possible that you may already be able to upload long videos. Check the “Longer videos” section in your Account Features page to check if the feature’s already enabled.
I already verified my account but I can’t upload long videos.
If you used to be able to upload long videos and no longer can, check your account for copyright claims and strikes.
My video is larger than 128GB.
If your video is larger than 128GB, try compressing your video in a video editor before uploading it to YouTube. This will reduce your video file size, while still keeping the video quality high. One common way to compress a video for YouTube is to encode it using the H.264 codec.
SOURCE: Google Support.