How to Make YouTube Shorts from Existing Videos — Step-by-Step

YouTube Shorts has exploded in popularity since its launch, accumulating over 50 billion daily views globally. For content creators, Shorts represent one of the most effective growth channels available — and the best part is, you don't need to create entirely new content. You can repurpose your existing long-form videos into engaging Shorts in just minutes.

In this guide, we'll show you exactly how to transform any YouTube video into a perfectly formatted Short using free online tools, and share strategies for selecting the best moments that drive maximum engagement.

What Are YouTube Shorts?

YouTube Shorts are vertical videos (9:16 aspect ratio) that are 60 seconds or less. They appear in a dedicated Shorts shelf on YouTube's homepage and in the Shorts tab on channels. Key specifications include:

• Maximum Length: 60 seconds
• Aspect Ratio: 9:16 (vertical / portrait)
• Resolution: 1080 x 1920 pixels (recommended)
• Format: MP4 (standard)

Shorts are served through YouTube's algorithm in a TikTok-style scrolling feed, giving them massive organic reach potential — often reaching viewers who have never seen your channel before.

Why Repurpose Long Videos into Shorts?

Creating Shorts from existing content is one of the smartest strategies in content creation today. Here's why:

• Massive Reach: Shorts can reach millions of viewers through YouTube's recommendation algorithm, far beyond your existing subscriber base.
• Time Efficiency: Instead of filming, editing, and producing entirely new content, you extract the best moments from videos you've already created.
• Cross-Platform Content: A 9:16 vertical clip works on YouTube Shorts, TikTok, Instagram Reels, and Facebook Reels — one clip, four platforms.
• Drive Long-Form Views: Shorts act as trailers or teasers that drive curious viewers to your full-length videos, increasing watch time and subscriber counts.
• Monetization: YouTube's Shorts monetization program shares ad revenue with creators, meaning your repurposed clips can directly generate income.

How to Create YouTube Shorts with VidsTrim

The fastest way to create Shorts from existing videos is using an online tool like VidsTrim, which handles both the trimming and the aspect ratio conversion in one workflow:

Step 1: Select Your Best Moment

Before you even open VidsTrim, watch your long-form video and identify the most engaging moment. Look for segments that are:

• Self-contained — they make sense without context from the rest of the video
• Emotionally engaging — funny, surprising, educational, or thought-provoking
• Under 60 seconds — ideally 15-30 seconds for maximum retention
• Visually interesting — good facial expressions, demonstrations, or action

Note the timestamp (minute:second) of the start and end of your chosen segment.

Step 2: Load and Trim the Video

Go to vidstrim.online, paste your YouTube URL, and click "Load Video." Use the timeline slider or manual time inputs to set your start and end points to the segment you identified. Make sure the total duration is 60 seconds or less.

Step 3: Select Portrait Aspect Ratio

In the Output Format section, set the Aspect Ratio to "9:16 (Portrait)". This tells VidsTrim that you want to convert the clip from standard 16:9 landscape format to vertical portrait format.

Step 4: Trim the Video

Click "Trim Video" and wait for processing. Once complete, VidsTrim will display the Aspect Ratio Cropping section with a visual preview of your trimmed clip.

Step 5: Position the Crop Area

This is where the magic happens. The crop preview shows your video with a vertical crop area overlay. Drag the crop area left or right to position it over the most important part of the frame — typically the speaker's face, a product demonstration, or the main action.

The visual preview lets you play the video to make sure the crop captures the right area throughout the entire clip. If the subject moves around, position the crop to capture the area where they spend most of the time.

Step 6: Apply and Download

Click "Apply Crop & Download" to get your perfectly formatted 9:16 Short. The file is ready to upload directly to YouTube Shorts, TikTok, Instagram Reels, or any other vertical video platform.

Content Selection Strategies for Maximum Engagement

Not every moment from a long video makes a good Short. Here are proven strategies for selecting clips that perform well:

The "Hook First" Strategy

Shorts need to capture attention in the first 1-2 seconds. Pick moments that start with a strong hook — a surprising statement, an unexpected visual, or a compelling question. The viewer decides whether to keep watching or swipe away in under 2 seconds, so the opening is everything.

The "Satisfying Completion" Strategy

Viewers love clips that have a clear beginning, middle, and end within the short format. A complete thought, a finished demonstration, or a resolved question creates a satisfying viewing experience that encourages likes and shares.

The "Cliffhanger" Strategy

End your Short at a moment of peak curiosity, then add a text overlay or verbal call-to-action like "Watch the full video for the answer!" This drives viewers from your Short to your long-form content, boosting watch time and engagement across your channel.

The "Series" Strategy

From one long video, create a numbered series of Shorts: "Part 1," "Part 2," "Part 3." This creates anticipation and gives viewers a reason to follow your channel for the next installment.

Best Practices for YouTube Shorts

• Optimal Length: While Shorts can be up to 60 seconds, analytics consistently show that 15-30 second clips get the highest retention rates and algorithm boost.
• Add Captions: Over 80% of social media video is watched without sound. Adding captions (even manually in your full editor) dramatically increases engagement and accessibility.
• Use #Shorts: Include #Shorts in your title or description to help YouTube's algorithm identify your video as a Short.
• Consistent Posting: Upload 3-5 Shorts per week for optimal algorithm performance. Repurposing existing content makes this sustainable without burning out.
• Vertical Only: Always use 9:16 aspect ratio. Horizontal or square clips in the Shorts feed look unprofessional and get significantly lower engagement.
• Engaging Thumbnails: YouTube auto-selects a thumbnail for Shorts, but you can change it. Choose a frame with clear facial expression or action.

Platform Cross-Posting Guide

One of the biggest advantages of creating 9:16 vertical clips is that the same file works across multiple platforms. Here's a quick reference for cross-posting your Shorts:

• YouTube Shorts: Max 60 seconds, 9:16 ratio, MP4 format. Upload through YouTube Studio or the YouTube app.
• TikTok: Max 10 minutes (but short clips perform best), 9:16 ratio. Upload through the TikTok app.
• Instagram Reels: Max 90 seconds, 9:16 ratio. Upload through the Instagram app.
• Facebook Reels: Max 90 seconds, 9:16 ratio. Upload through the Facebook app.

For a deeper comparison of these platforms, read our YouTube Shorts vs TikTok vs Reels comparison guide.

Conclusion

Creating YouTube Shorts from existing videos is the most efficient content strategy available to creators today. With tools like VidsTrim, the entire process — from YouTube URL to uploaded Short — takes just a few minutes. No desktop software, no complex editing, no watermarks.

Start by identifying 3-5 highlight moments from your best-performing videos, trim and crop them with VidsTrim, and upload them as Shorts. You'll be amazed at the reach and new subscribers these small clips can generate.

→ Try VidsTrim now and create your first Short