YouTube doesn't provide a method for uploading a fixed or edited video in place of an existing upload, so you can't move existing comments, likes and favorites to a new upload. Thankfully, you have a few other options. Upload a replacement and link to it in your old video or use YouTube's enhancement tools to make minor changes.
Upload a Replacement
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A new upload can't actually replace an existing video, so use annotations to redirect viewers from your old video to the new copy.
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Step 1: Upload the New Video
Upload the new copy of your video the same way you uploaded the original: Click Upload on YouTube and drag your new video file into the YouTube window. Give your new video any name and description you want; it doesn't have to match the original exactly. Wait until the upload finishes and copy the address of the new video.
Step 2: Edit Annotations
Open your old video and click Annotations.
Step 3: Add an Annotation
Pause the video at its beginning on the Annotations screen. Click Add Annotation and choose Note.
Step 4: Link to the New Video
Write a note directing viewers to click to see the new video. Use the size and color settings to help your message stand out. Check Link and paste the full address of your new video in the box.
Step 5: Extend the Annotation
Drag the right edge of the annotation on the timeline to the right to extend its duration. Leave the annotation up for at least several seconds so that viewers have time to read and click it. If you want, leave it up for the entire duration of the video. Click Apply Changes to finish.
Fix a Video Using Enhancements
YouTube's enhancement tools can fix minor problems in a video without requiring a new upload. This method doesn't change the video's address, but also doesn't offer the versatility of a full video editor.
Step 1: Open Enhancements
Open your video on YouTube while logged in, and click Enhancements.
Step 2: Make Changes
Apply enhancements such as color adjustments, slow motion, time lapse or image stabilization. Use the arrows to rotate the video or click Trim to cut out part of the video. When you're finished, press Save.