Video Aspect Ratio Changer - Free Online Tool

Change video aspect ratio to 16:9, 4:3, 1:1, 9:16, or custom ratios. Letterbox, crop, or stretch modes. Preview before processing. Browser-based, no uploads.

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All processing happens in your browser using FFmpeg WebAssembly. Your videos never leave your device—completely private and secure.

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Frequently Asked Questions

Aspect ratio is the proportional relationship between a video's width and height, expressed as two numbers separated by a colon (e.g., 16:9). Common ratios include 16:9 for widescreen, 4:3 for traditional TV, 1:1 for Instagram posts, 9:16 for vertical mobile video, and 21:9 for ultrawide cinematic. The ratio determines the video's shape and how it displays on different screens and platforms.

Letterbox mode adds black bars (horizontal or vertical) to preserve the entire original video without distortion. Crop mode cuts portions of the video edges to fill the new aspect ratio, potentially losing content but avoiding black bars. Stretch mode distorts the video by expanding or compressing it to fit the new dimensions, which can make subjects appear unnaturally wide or tall. Choose based on whether you prioritize preserving content, avoiding bars, or avoiding cropping.

Use letterbox when you need to preserve all video content and don't mind black bars—ideal for archival, presentations, or when important content fills the frame edges. Use crop when the video has safe margins around key subjects and you want a polished look for social media—most content platforms prefer videos without black bars for better engagement.

YouTube and most video players use 16:9 widescreen. Instagram feed posts work best at 1:1 square or 4:5 portrait. TikTok, Instagram Reels, and YouTube Shorts require 9:16 vertical video. Facebook supports multiple ratios but 1:1 performs well in feeds. Twitter video works at 16:9 or 1:1. For cinematic content, 21:9 ultrawide creates a theatrical feel. Always check platform guidelines as requirements evolve.

Letterbox mode maintains original quality since it only adds padding without re-encoding the video itself (though FFmpeg still processes it). Crop mode also preserves quality as it extracts a portion of the original resolution. Stretch mode can reduce perceived quality because it distorts pixels, making circular objects oval and affecting spatial relationships. For best quality, avoid stretch mode and use source material with higher resolution than your target.

Yes, the custom option lets you specify any width and height ratio. Common custom ratios include 2:1 for panoramic displays, 3:2 for photography-style video, and 2.35:1 or 2.39:1 for anamorphic widescreen. Enter the width value in the first field and height value in the second. The tool will calculate and apply the exact ratio you specify.

This tool adds black bars (letterboxing or pillarboxing) by default, which is the cinema standard. Black bars work universally because they don't distract from content and blend with most display bezels. Some professional workflows use custom bar colors for branding, but black remains the safest choice for compatibility and viewer experience.

No, aspect ratio changes only affect the video dimensions and framing. Audio tracks are copied without modification, maintaining original quality, synchronization, and duration. All three modes (letterbox, crop, stretch) preserve audio exactly as it was in the source file.

Processing happens in your browser using FFmpeg WebAssembly. Most videos up to 500MB work smoothly. Larger files may process slowly or encounter memory limits depending on your device's RAM and CPU. If you experience issues with large files, try trimming them first or using a device with more memory.

Yes, after uploading your video and selecting settings, the preview section shows how your video will look with the new aspect ratio. You can play the preview to check framing and ensure important content isn't cropped or bars are positioned correctly. Only proceed to process when you're satisfied with the preview.

Video Aspect Ratio Changer - Free Online Tool

Original Aspect Ratio

New Aspect Ratio

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