If your child is old enough to have a smartphone, chances are good that he or she also uses - or at least wants to download - TikTok, a video-sharing app based on one simple rule: Posts have to be under 15 seconds long.

In 2018, the social media platform beloved by teens around the world said it hit more than half a billion active users worldwide, making it the fastest-growing platform that isn't owned by Facebook.

As with many social media apps, TikTok users typically spend close to an hour a day on this notoriously addictive platform, according to mobile industry researcher Business of Apps.

If you're worried your child is spending too much time swiping through videos of other teens lip-syncing pop songs, it might be a good idea to talk to them about turning on the app's built-in time limits.

TikTok's Screen Time Management function, which can be found in the privacy and settings options under the section Digital Wellbeing, will let you set a daily time limit of 40,60,90 or 120 minutes.

Once the time is used up, a password needs to be entered to continue using the app.

To make sure your child is only seeing age-appropriate content in the app, you can also activate the Restricted Mode, which TikTok says will limit the appearance of content that may not be appropriate for all audiences.

Why you should take a look at your child's privacy settings on TikTok

The TikTok app is used by tens of millions of children around the world. Parents would be wise to take a closer look at the privacy settings to prevent unwanted contact from strangers or sudden expenses for parents.

The most important thing to do is to set the child's profile to private. That ensures that their posts on the short video platform can only be seen by people who they've allowed to follow them.

To protect against unwanted contact by strangers it's also recommended to choose the option that means only friends can send you messages or leave comments on your videos.

The app allows you to give away virtual gifts known as gift points but these cost real money. Experts recommend that parents decide beforehand whether they're going to allow their children to do this.

TikTok users are supposed to be at least 13-years-old to use the app, but no real age checking takes place.

Setting general time limits on a smartphone

You can also set limits across all apps, not just TikTok, using tools from Google and Apple to help users reduce screen time.

"The latest releases of iOS and Android come with convenient statistics capabilities on board. With the help of so-called screen time assistants, users can monitor how many minutes, hours or days they have spent on apps," says app specialist Andreas Weck.

For Android, this feature has been integrated since Android 9 (Pie). Users can find it in the settings under Digital Wellbeing. For older operating systems, the app can be downloaded from the Google Play Store.

"On the overview page, you can see how long you have used the smartphone so far or how long the screen was switched on," says smartphone expert Alexander Kuch.

You can set a maximum time limit to spend on an app, and if you use your smartphone a lot in the evenings, there's also relaxation mode to counteract this - at the time you set, the colours on the display will be replaced by greyscale.

On Apple devices, the comparable feature is called Screen Time and has been around since iOS 12. It can be found under settings and shows daily usage broken down by apps and websites.

The Downtime feature allows you to set a schedule for screen-free time. You can also use the App Limits feature to set daily time limits on app categories such as social networks, games or entertainment.The idea behind all of these features is that by seeing how long you spend on your smartphone, you can think about your habits and change your behaviour if necessary.

 - dpa