Resize / Crop Video
Upload a video and resize it to any resolution — processed locally in your browser.
Resolution
All processing happens in your browser — your files are never uploaded.
How to use Resize / Crop Video
The Resize Video tool scales an MP4, WebM or MOV video to a new resolution — from a 4K source down to 1080p, 720p or a custom size — or crops it to a specific aspect ratio such as 16:9, 9:16 or 1:1 for social media platforms, all processed locally in your browser with no file uploads. Use it to prepare footage for Instagram Reels, YouTube Shorts, TikTok, Twitter or any platform with specific resolution requirements.
- Click "Select Video" and open your MP4, WebM or MOV source file.
- Choose a preset resolution (4K, 1080p, 720p, 480p) or enter a custom width and height.
- Select the scaling mode: "Fit" to letterbox/pillarbox, "Fill" to crop to the target aspect ratio, or "Stretch" to ignore aspect ratio.
- If cropping, drag the crop region in the preview to position the frame exactly.
- Click Resize and download the scaled video once exporting completes.
Your data never leaves your device — 100% private processing.
Scaling, cropping and aspect ratios
Scaling reduces or increases the dimensions of every frame while maintaining the aspect ratio. Cropping removes pixels from the edges of the frame to fit a different aspect ratio. "Fit" mode adds black bars (letterbox for wide-to-tall, pillarbox for tall-to-wide) to avoid cropping any content. "Fill" mode crops symmetrically to fill the target frame entirely. For social media, fill-mode 9:16 is correct for TikTok and Instagram Reels, 1:1 for Instagram feed posts, and 16:9 for YouTube.
| Platform | Aspect ratio | Typical resolution |
|---|---|---|
| YouTube | 16:9 | 1920×1080 or 3840×2160 |
| Instagram feed | 1:1 or 4:5 | 1080×1080 or 1080×1350 |
| Instagram Reels / TikTok | 9:16 | 1080×1920 |
| Twitter / X | 16:9 | 1280×720 |
| 16:9 or 1:1 | 1920×1080 |
Maintaining quality when downscaling
Downscaling a video always involves re-encoding, which introduces some quality loss. To minimise this, use the highest quality CRF setting that still meets your target file size. The Lanczos algorithm is used for spatial scaling because it produces sharper results than bilinear or bicubic filters while suppressing ringing artefacts. Avoid upscaling: enlarging a video beyond its original resolution does not add detail and wastes bitrate on artificially large frames.
Glossary
- Aspect ratio
- The proportional relationship between a video frame's width and height, expressed as W:H (e.g. 16:9 or 9:16).
- Letterboxing
- Adding horizontal black bars above and below a widescreen video when displaying it in a taller frame to preserve the original aspect ratio.
- Pillarboxing
- Adding vertical black bars on the sides of a portrait or square video when displaying it in a wider frame to preserve the original aspect ratio.
- Lanczos scaling
- A high-quality resampling algorithm used for image and video resizing that produces sharp output with minimal blurring.
- Resolution
- The dimensions of a video frame measured in pixels (width × height); higher resolution means more detail and larger file size.
Related reading
Frequently Asked Questions
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Why use Resize / Crop Video?
- Powered by FFmpeg running directly in the browser — no upload needed
- Supports all major video and audio formats
- Lossless and lossy options for quality control
- Export results immediately without waiting for cloud processing
Common use cases
- Compress a video before uploading to Google Drive
- Extract audio from a video lecture for easy listening
- Trim a video clip for a social media reel
- Convert MOV files to MP4 for cross-platform compatibility
- Merge two audio tracks for a podcast episode
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