This article explains how to record a video on Instagram without having to press any buttons.
Steps
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Step 1. Open Instagram
The icon depicts a retro colored camera.
If prompted, enter your username and password, then tap "Login"
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Step 2. Tap the Home button in the lower left to view the feed
This page opens automatically upon login
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Step 3. Tap the camera button on the top left
You can also access it by swiping your finger from left to right across the screen
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Step 4. Tap Without holding
This option is located on the far right below the shutter button.
To see this option you need to slide your finger to the left
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Step 5. Tap the button that allows you to take photos and videos
As soon as you tap it Instagram will start recording. Tap it again to stop recording.