This tutorial assumes that you already have uploaded the video to your YouTube channel and that you do not already have a written transcript of the audio from your video. If you have an .srt file that you need to synchronize with your video, use the Adding Caption Files to YouTube Videos tutorial instead. If you already have a transcription prepared as a .txt file, use the Making Captions from Transcripts in YouTube. If you would like to create the captions from scratch yourself, use Creating Captions in YouTube from Scratch.
*Note: YouTube auto-generated captions that have not been corrected are insufficient. Steps 4-7 in this tutorial tell you how to correct the automatic captions. The FCC standards for captioning state that you must have an accuracy rate of 99% at the minimum. The typical accuracy of YouTube captions is well below that. If you intend to use the following approach, you must extensively review the auto-generated captions to ensure that there are no remaining errors.
Click on the drop-down list next to the Edit button for your video, and select Subtitles & CC.
On your video page, click on the caption file already present on the right called English (Automatic).
Click the Edit button in the top-right corner to modify the captions.
To edit the content of the captions, select the caption you'd like to edit left of the video and start typing.
You can adjust the start and end times of each caption at the bottom of the screen by clicking & dragging on the edges of the white boxes. The audio signal is shown in grey behind the white text boxes to help find where the audio begins and ends.
Hit Shift-Enter to add a line break; you should have no more than 2 lines of text in your captions. Try to divide your caption blocks at the start or end of complete phrases so that users don’t have to retain detailed information across caption blocks.
When finished, click Publish in the top right corner to finalize the captions.