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How to Resize Video for Instagram, TikTok, and YouTube

Every platform wants different dimensions, aspect ratios, and file sizes. Here is a complete reference for video specs on every major social platform, plus how to resize locally without uploading to a web tool.

Why video dimensions matter for social media

Social media platforms are strict about video specs. Upload a horizontal 1920x1080 video to Instagram Reels and it gets cropped to 9:16, chopping off the sides. Upload a 4K file to Twitter/X and it gets re-encoded to a lower quality than if you had uploaded at 1280x720. Each platform has its own rules, and ignoring them means lost quality, awkward cropping, or rejected uploads.

The problem is worse for creators who publish the same content across multiple platforms. A single video needs to exist in three or four different dimensions. Doing this manually in a video editor is tedious. ConvX handles it from the command line in seconds.

Platform video specifications (2026)

These are the recommended upload specifications for each platform. Meeting these specs gives you the best quality after the platform re-encodes your upload.

For official and frequently updated guidelines, see Instagram's video requirements, YouTube's recommended upload settings, and TikTok's creator guidelines.

Understanding aspect ratios

Aspect ratio is the proportional relationship between width and height. Getting it right prevents awkward cropping.

The 4:5 ratio is often overlooked. On Instagram Feed, 4:5 videos take up more screen real estate than square (1:1) videos, which can improve engagement. It is the tallest ratio Instagram allows in the main feed.

Codec and encoding recommendations

Resolution is only half the equation. The codec, bitrate, and frame rate affect the final quality after the platform re-encodes your upload.

Codec: H.264 is the safest choice. Every platform accepts it. H.265 is accepted by some platforms (YouTube, TikTok) but may cause issues on Twitter/X and LinkedIn. Stick with H.264 unless you have a specific reason to use H.265.

Bitrate: Upload at the highest reasonable bitrate. The platform will re-encode your video regardless. Starting with a high-quality source gives the platform's encoder more data to work with, producing a better result after re-encoding.

Frame rate: Match your source. If you shot at 24 fps, upload at 24 fps. If you shot at 30 fps, upload at 30 fps. Converting 24 fps to 30 fps introduces judder. YouTube and TikTok support 60 fps for smooth motion (gaming content, sports). Instagram Reels caps at 30 fps internally even if you upload 60 fps.

Audio: AAC, 128 kbps stereo minimum. 256 kbps if the video has music. All platforms accept AAC. Some accept Opus, but AAC is the safer choice.

Resizing with ConvX

ConvX provides two approaches: presets for common platforms, and manual dimensions for full control. See all available flags in the CLI reference.

Using presets

convx convert clip.mp4 --preset instagram-reel

Presets apply the correct resolution, aspect ratio, frame rate, and bitrate for a specific platform. No need to remember specs. ConvX includes presets for the most common targets:

• --preset instagram-reel (1080x1920, 9:16, 30 fps, H.264)
• --preset instagram-feed (1080x1350, 4:5, 30 fps, H.264)
• --preset instagram-square (1080x1080, 1:1, 30 fps, H.264)
• --preset tiktok (1080x1920, 9:16, 30 fps, H.264)
• --preset youtube-shorts (1080x1920, 9:16, 30 fps, H.264)
• --preset youtube-1080 (1920x1080, 16:9, 30 fps, H.264)
• --preset youtube-4k (3840x2160, 16:9, 30 fps, H.264)
• --preset twitter (1280x720, 16:9, 30 fps, H.264)

Using manual dimensions

convx convert clip.mp4 --width 1080 --height 1920 --fps 30

This gives you full control. Specify width, height, and frame rate independently. ConvX scales the video and adds letterboxing or pillarboxing if the source aspect ratio does not match the target. No content is cropped by default.

Handling aspect ratio mismatches

What happens when your source video is 16:9 horizontal but you need 9:16 vertical? There are three strategies.

Letterbox/pillarbox (default). ConvX fits the entire video inside the target dimensions and fills the remaining space with black bars. No content is lost, but you get bars on the sides (pillarbox) or top/bottom (letterbox). This is the safest option.

Crop to fill. ConvX scales the video to fill the target dimensions completely, then crops the overflow. Content at the edges is lost. This produces a full-bleed video with no bars, but you must verify that important content is not cut off.

convx convert clip.mp4 --width 1080 --height 1920 --crop fill

Stretch (not recommended). ConvX stretches the video to fit, distorting the proportions. People look wider or taller. This almost always looks bad. Avoid it unless you have a very specific reason.

Batch resizing for multiple platforms

If you create content for multiple platforms, you need the same video in several sizes. Run multiple preset conversions in sequence:

convx convert clip.mp4 --preset instagram-reel -d ./output
convx convert clip.mp4 --preset youtube-1080 -d ./output
convx convert clip.mp4 --preset twitter -d ./output

Each command produces a separate output file named with the preset suffix. From one source video, you get platform-ready files for Instagram, YouTube, and Twitter in under a minute.

For a folder of clips:

convx convert clips/ --preset tiktok -j 4 -d ./tiktok-ready

Converts every video in the clips/ directory to TikTok's vertical format using 4 parallel jobs.

File size limits and compression

Twitter/X has the strictest file size limit at 512 MB. TikTok allows 4 GB on mobile and 10 GB on web. YouTube is extremely generous at 256 GB. For most creators, file size only becomes an issue on Twitter/X.

If your video exceeds a platform's limit, reduce the quality:

convx convert clip.mp4 --preset twitter -q 70

Quality 70 typically produces a file that is 40 to 60% smaller than quality 100 with no visible difference on Twitter's compressed playback. For more aggressive compression strategies, see our guide on compressing video for Discord, which covers similar file size constraints.

Vertical video from horizontal footage

This is the most common resizing task. You shot a video in landscape (16:9) and now you need a vertical (9:16) version for Reels or TikTok.

Option 1: center crop. Take the center portion of the horizontal frame and crop it to 9:16. This works well when the subject is centered. The left and right edges are lost.

convx convert landscape.mp4 --width 1080 --height 1920 --crop fill

Option 2: pillarbox. Show the full horizontal video with black bars on top and bottom. No content is lost, but the video appears smaller on the viewer's screen, reducing impact.

convx convert landscape.mp4 --width 1080 --height 1920

Option 3: blur fill. Show the full horizontal video in the center with a blurred, zoomed version of the same video as the background. This is the technique Instagram and TikTok use when you upload horizontal content. It fills the vertical frame without black bars and without cropping.

convx convert landscape.mp4 --width 1080 --height 1920 --bg blur

The blur fill option produces the most professional-looking result for horizontal-to-vertical conversion. It avoids the dead space of pillarboxing and the information loss of cropping.

Horizontal video from vertical footage

The reverse situation: vertical footage needs to go on YouTube's standard 16:9 player. The same three options apply. Center crop loses the top and bottom. Letterboxing adds black bars on the sides. Blur fill works here too, placing the vertical video in the center with blurred content filling the horizontal frame.

convx convert vertical-clip.mp4 --width 1920 --height 1080 --bg blur

Using the desktop app

Drag your video into ConvX. Select a platform preset from the dropdown, or enter custom dimensions. The preview shows how the output will look, including any letterboxing or cropping. Adjust the crop position by dragging the frame overlay. Click convert. The desktop app is particularly useful for crop-to-fill operations where you need to see exactly what content will be preserved.

Using ConvX with AI agents via MCP

Content creators using AI assistants can automate multi-platform publishing workflows. An AI agent with access to the ConvX MCP server can take a single source video, resize it for every platform, and prepare the files for upload, all in one automated sequence.

Platform-specific tips

Instagram

Instagram re-encodes everything. Upload the highest quality you can. For Reels, 1080x1920 at 30 fps with H.264 and 10+ Mbps bitrate gives the best result after Instagram's re-encoding. Cover images for Reels are extracted from the video; there is no way to upload a separate thumbnail on mobile. Frame your key moment accordingly.

TikTok

TikTok accepts up to 4K but downscales to 1080p for delivery. Uploading at 1080x1920 is sufficient. TikTok's compression is aggressive, especially on mobile uploads. Uploading via the web (tiktok.com) often produces better quality than the mobile app because the web uploader accepts larger files and applies less compression.

YouTube

YouTube processes uploaded videos through multiple encoding passes. Higher resolution uploads (4K) result in the VP9 codec being used for delivery, which looks better than the AVC encoding used for 1080p uploads. If you want the best quality on YouTube, upload at 4K even if your source is 1080p. YouTube's encoder produces a better-looking 1080p stream from a 4K upload than from a 1080p upload. This is a well-known trick among YouTube creators.

Twitter/X

Twitter's 2 minute 20 second limit and 512 MB cap are the most restrictive among major platforms. Twitter also re-encodes aggressively. For the best results, upload at 1280x720 (720p) with H.264. Twitter's encoder handles 720p better than 1080p in many cases because it allocates fewer bits per pixel at higher resolutions. Keep bitrate under 8 Mbps to avoid exceeding the file size limit on longer clips.

Troubleshooting

Video looks blurry after uploading to Instagram

Instagram compresses uploaded videos heavily. The most common cause of blurriness is uploading a video that was already compressed once. Each compression cycle degrades quality. Start with the highest quality source file you have. Upload at 1080x1920 with at least 10 Mbps bitrate. Also ensure you are uploading via a stable internet connection; Instagram may reduce upload quality on slow connections.

Black bars appear on the video

Your source video's aspect ratio does not match the target platform. If you used the default letterbox/pillarbox mode, black bars are added to fill the frame. Use --crop fill to crop to the exact dimensions instead, or --bg blur for a blur-filled background. Verify the result to ensure important content is not cut off.

Video is cropped differently than expected

When using --crop fill, ConvX centers the crop by default. If your subject is not centered, the crop may cut off important content. Use the desktop app's visual crop overlay to position the crop area manually. In the CLI, use --crop-gravity with values like top, bottom, left, or right to shift the crop position.

Upload rejected by the platform

Common reasons: file too large (check the platform's size limit), video too long (check the duration limit), unsupported codec (use H.264 with AAC audio), or frame rate too high (some platforms cap at 30 fps for certain formats). ConvX presets handle all of these constraints automatically. If you used manual settings, verify against the specifications table above.

Audio quality dropped after resizing

Resizing the video triggers a full re-encode, which also re-encodes the audio. ConvX defaults to 192 kbps AAC, which is sufficient for social media. If your source has high-quality music, increase the audio bitrate: --audio-bitrate 256k. Note that social platforms re-encode audio on their end regardless, so uploading at 256 kbps provides a better source for their encoder.

Colors look washed out or different

This can happen when the source video uses a color space (like HDR/Rec. 2020) that the encoder converts to SDR/Rec. 709 during processing. Social media platforms do not support HDR playback (with the exception of YouTube, which supports HDR for some content). ConvX converts HDR to SDR with tone mapping to preserve the visual look. If colors still appear off, the issue may be the platform's own re-encoding. Upload a short test clip to verify before processing your full video.

Related articles

• How to Compress Video for Discord Under 25MB
• How to Convert MOV to MP4 on Mac, Windows, and Linux
• How to Convert WebM to MP4