TikTok began rolling out a new text-to-speech feature this week that will automatically convert text to a voiceover as users watch videos that have the feature enabled. Our guide will show you how to activate text-to-speech on your videos before posting them.
Note: These screenshots were captured in the TikTok application on iOS.
Step 1: Once you’ve recorded or uploaded a video in TikTok, tap the “Text” button at the bottom of the screen.

Step 2: Type your desired text, and then tap “Done” in the top-right corner of the screen.

Step 3: Tap the text you typed.

Step 4: Tap “Text-to-speech.” This will cause the application to convert this text to speech that becomes part of the video’s audio.

From there, you can continue editing your post as normal.
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