Will resizing reduce file size?

Yes, reducing resolution generally reduces file size significantly since fewer pixels means less data to encode.

Does downscaling reduce quality?

Shrinking resolution discards pixels, but because the image is smaller the loss is usually invisible at the new size. High-quality Lanczos filtering keeps downscaled video sharp; upscaling, by contrast, cannot add real detail and tends to look soft.

What is the difference between Fit, Fill and Stretch?

Fit letterboxes or pillarboxes to show the whole frame with bars; Fill crops to fill the target aspect ratio with no bars; Stretch ignores aspect ratio and distorts the image. Fill is usual for social crops, Fit when you must keep the entire frame.

How do I make a video vertical for Reels or TikTok?

Choose a 9:16 target and use Fill, then drag the crop region in the preview to keep the important action centered. This turns landscape 16:9 footage into a full-screen vertical clip without bars.

What resolution should I export for social media?

Use 1080×1920 for vertical Reels, TikTok and Shorts, 1080×1080 for square feed posts, and 1920×1080 for standard landscape. Picking the platform native resolution avoids extra re-compression when you upload.

Can I resize without changing the aspect ratio?

Yes. Enter a width and height that keep the original ratio (e.g. 1920×1080 to 1280×720) and the frame scales cleanly with no cropping or distortion. Fit mode also preserves the ratio by adding bars if the target differs.

Is the video uploaded to resize it?

No. Resizing runs through FFmpeg in WebAssembly in your browser, so footage never leaves your device. Speed depends on your CPU and the clip size — a long 4K source is memory-bound and slower on phones than on desktops.

Resize Video Online — Change Video Resolution

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.

Common video aspect ratios by platform
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
LinkedIn	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.

Worked examples

Downscale to 720p

Inputs: 1920×1080 source → 720p

Result: 1280×720 video

4K to 1080p

Inputs: 3840×2160 source → 1080p

Result: 1920×1080 video

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 Audio & Video

Video to GIF Converter

Convert any video clip to an animated GIF. Set the duration, frame rate, and width to create the perfect shareable GIF — right in your browser.

Change Audio/Video Volume

Increase or decrease the volume of any audio or video file online. Adjust volume from silent to 200%, processed in your browser.

Video Compressor

Compress video files online without losing quality. Reduce MP4, WebM, and other video file sizes directly in your browser.

Video Converter

Convert videos between MP4, WebM, AVI, and MOV in your browser with private processing, quick exports, and no file uploads.

Merge / Join Videos

Merge and join multiple video files into one online. Combine MP4, WebM, and other videos directly in your browser — free, private, with no upload.

Video to MP3 Converter

Extract audio from video files and convert to MP3 directly in your browser. No uploads, no sign-up, and instant local processing.

Explore all Audio & Video.

Resize / Crop Video

How to use Resize / Crop Video

Scaling, cropping and aspect ratios

Maintaining quality when downscaling

Worked examples

Glossary

Related reading

Frequently Asked Questions

Why use Resize / Crop Video?

Common use cases

Get weekly tool tips & updates

Related Audio & Video