Best Video Lengths for TikTok App Ads (2025)

TikTok allows video ads from 5 to 60 seconds. That's a wide range, and it matters.

Completion rate drops by 10% for every 5 seconds of runtime. Longer videos give users more time to scroll, which kills engagement and drives up CPIs.

The optimal length is 9-15 seconds. Here's why, and how to structure videos at this duration.

TikTok's Technical Specs

TikTok supports video lengths between 5 and 60 seconds for in-feed ads.

Technical requirements:

• Minimum: 5 seconds
• Maximum: 60 seconds
• Recommended by TikTok: 21-34 seconds

But TikTok's official recommendation doesn't align with performance data. Their 21-34 second guidance optimizes for storytelling depth, not for paid ad efficiency.

What the Data Shows: 9-15 Seconds Wins

Multiple performance analyses show that 9-15 seconds delivers the best results for app install ads.

Why this range works:

9 seconds: Long enough to deliver a hook (3 seconds), one clear benefit (4 seconds), and a CTA (2 seconds).

15 seconds: Enough time for a hook, a quick demonstration or testimonial, and a close—without overstaying attention.

Anything shorter than 9 seconds feels rushed. Anything longer than 15 seconds risks user drop-off.

The Completion Rate Problem

Users don't watch full videos on TikTok. They scroll.

Only 55% of users watch videos to completion on average. That drops 10% for every additional 5 seconds.

What this means in practice:

• 10-second video: 55% completion rate
• 15-second video: 45% completion rate
• 20-second video: 35% completion rate
• 30-second video: 15% completion rate

Completion rate correlates directly with performance. Videos users finish are more likely to drive clicks and installs. Videos they scroll past don't convert.

How to Structure Videos at 9-15 Seconds

Short-form content requires aggressive editing. Every second needs a purpose.

Framework for 9-second videos:

• 0-3 seconds: Hook (visual or verbal pattern interrupt)
• 3-7 seconds: One clear benefit or demonstration
• 7-9 seconds: CTA (Install now, Download, Try it free)

Framework for 15-second videos:

• 0-3 seconds: Hook
• 3-8 seconds: Problem/solution or before/after
• 8-13 seconds: Social proof or secondary benefit
• 13-15 seconds: CTA

The structure is straightforward: grab attention, deliver one idea, close. No fluff.

When Longer Videos Work

There are exceptions where longer videos (20-30 seconds) can perform well:

1. Complex apps requiring explanation

If your app solves a non-obvious problem or requires setup context, 20-25 seconds gives you room to explain without rushing.

2. Storytelling-driven creatives

Testimonials or user stories sometimes need more time to build emotional connection. A 30-second before/after transformation can work if the story is compelling.

3. Spark Ads with proven organic performance

If an organic video performed well at 25 seconds, don't cut it down just to hit a shorter benchmark. Promote what's already working.

Key principle:

Use longer videos only when the content justifies it. Don't add length for the sake of it.

When Shorter Videos Work

Videos under 9 seconds can work in specific situations:

1. Single-message ads

If your entire pitch is "Track workouts in 10 seconds," you don't need 15 seconds to communicate it. A 7-second video might be perfect.

2. Visual-first demos

If the app's value is immediately obvious from a quick screen recording (e.g., a dramatic before/after visual), shorter videos can work.

3. Retargeting ads

Users who already know your app don't need full context. A 6-8 second reminder with a CTA can be effective for re-engagement.

Limitation:

Very short videos (5-8 seconds) often feel abrupt. Unless the concept is extremely simple, stick with 9-15 seconds for better pacing.

Video Length and Platform Behavior

TikTok's algorithm rewards engagement, and engagement correlates with completion.

If users consistently watch your video to the end, TikTok interprets that as a quality signal and shows it to more people. This lowers your CPM and CPI.

Conversely, if users scroll past your video at the 5-second mark, TikTok reduces distribution. Your costs rise.

Implication:

Shorter videos that hold attention outperform longer videos that lose it. A 12-second video with 60% completion will beat a 30-second video with 20% completion every time.

Testing Video Length

Don't assume one length works for all apps. Test it.

How to test:

1. Create the same ad concept in three lengths: 9 seconds, 15 seconds, 21 seconds
2. Keep the hook and message identical—only vary the length
3. Run all three in the same campaign for 7 days
4. Compare completion rate, CPI, and CTR

The version with the highest completion rate and lowest CPI wins. Use that length as your benchmark moving forward.

Common Mistakes with Video Length

1. Padding videos to hit a perceived ideal length

If your message takes 10 seconds, don't stretch it to 15 just to match a recommendation. Respect attention spans.

2. Cutting too much content

Rushing through your message to hit a short duration can make videos feel incoherent. If it takes 18 seconds to deliver clarity, use 18 seconds.

3. Ignoring the hook

No matter the length, the first 3 seconds determine if anyone watches the rest. A weak hook kills long and short videos equally.

4. Using one length for all creatives

Different messages and formats work at different lengths. Testimonials might need 20 seconds. Quick demos might only need 10. Match length to content.

Video Length Benchmarks (2025)

Video Length	Completion Rate	Best Use Case
5-8 seconds	60-70%	Simple, single-message ads
9-15 seconds	45-60%	Standard app install ads (optimal)
16-21 seconds	35-50%	Explainer content, complex value props
21-34 seconds	25-40%	Testimonials, storytelling ads
35-60 seconds	10-25%	Long-form organic content (rarely for paid ads)

Source: Industry benchmarks, TikTok performance data (2025)

Video Length Checklist

When planning your TikTok ad length:

• Does the message require more than 15 seconds, or can it be tightened?
• Is the hook strong enough to retain attention through the full duration?
• Have you tested different lengths to validate what works for your audience?
• Are you avoiding filler content just to hit a target length?
• Does completion rate stay above 40% for this video length?

FAQs

What's the best video length for TikTok app ads?

The optimal length is 9-15 seconds. While TikTok supports videos from 5-60 seconds, shorter videos consistently drive higher completion rates and better CPIs. TikTok officially recommends 21-34 seconds, but performance data shows 9-15 seconds works best for most app campaigns.

Do longer videos perform worse on TikTok?

Yes. Completion rate drops 10% for every 5 seconds of runtime. Longer videos give users more opportunities to scroll, which hurts engagement metrics and increases CPIs. Keep videos concise to maintain attention.

Should I use the full 60 seconds TikTok allows?

Almost never for paid ads. 60-second videos work for deep storytelling in organic content, but paid ads need to deliver value quickly. Users don't have the patience for long ads—they're scrolling for entertainment, not watching commercials.

How do I know if my video is too long?

Check completion rate. If it's below 40%, the video is likely too long or the pacing is off. High drop-off rates indicate users are losing interest before the video ends.

Can I use different video lengths in the same ad group?

Yes, and you should. Test multiple lengths (9s, 12s, 15s) within the same ad group to let TikTok's algorithm identify which duration performs best for your audience.

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Video length is one of the simplest variables to test and one of the highest-impact optimizations you can make. Start with 9-15 seconds, validate with your own data, and cut ruthlessly. Every second counts.