Viral Video Platform Specifications

Use this skill to choose export settings for TikTok, YouTube Shorts, Instagram Reels, Facebook Reels, Snapchat Spotlight, Twitter/X, Pinterest, LinkedIn, and mobile-browser playback. This SKILL is a lean orchestrator; detailed platform tables, commands, and recipes are preserved in references/platform-details-and-recipes.md.

Quick Reference

Platform	Aspect	Recommended resolution	Practical duration	Max size	Default codec
TikTok	9:16	1080x1920	21-34s	287 MB iOS	H.264 + AAC
YouTube Shorts	9:16	1080x1920	50-59s	256 GB	H.264 or VP9
Instagram Reels	9:16	1080x1920	7-30s	4 GB	H.264 + AAC
Facebook Reels	9:16	1080x1920	15-30s	4 GB	H.264 + AAC
Snapchat Spotlight	9:16	1080x1920	<=60s	300 MB	H.264 + AAC
Twitter/X	9:16, 16:9, 1:1	1080x1920	<=140s	512 MB	H.264 + AAC

Universal Social Export Baseline

ffmpeg -i input.mp4 \
  -vf "scale=1080:1920:force_original_aspect_ratio=decrease,pad=1080:1920:(ow-iw)/2:(oh-ih)/2:black,setsar=1,fps=30" \
  -c:v libx264 -preset medium -crf 22 -profile:v high -level 4.1 \
  -c:a aac -b:a 192k -ar 48000 -ac 2 \
  -pix_fmt yuv420p -movflags +faststart \
  output_social.mp4

Adjust loudness, duration, bitrate, and metadata per platform from the reference file.

Core Workflow

Verify ffmpeg -version; prefer current stable builds for security and codec fixes.
Identify target platform(s) and whether the video is native-app upload or mobile-browser playback.
Normalize to vertical 9:16 unless the platform or campaign calls for square/horizontal.
Use H.264/AAC for the broadest acceptance. Use VP9 only when intentionally targeting YouTube/WebM.
Apply platform loudness targets: TikTok/Reels often around -10 to -12 LUFS; YouTube around -14 LUFS; Facebook around -13 LUFS.
Keep -pix_fmt yuv420p and -movflags +faststart for compatibility.
Verify output with ffprobe before upload.

Key Gotchas

All major social platforms re-encode uploads; high-quality H.264 is usually a better upload source than HEVC/AV1 for social delivery.
For web/mobile-browser playback, profile/level, yuv420p, and faststart matter more than platform upload limits.
Keep captions and UI out of unsafe top/bottom regions, especially lower 35% on Reels-style interfaces.
Two-pass bitrate control is useful when a platform file-size ceiling is strict.

Reference Map

references/platform-details-and-recipes.md - Full preserved reference: per-platform spec tables, FFmpeg presets, two-pass examples, multi-platform export script, file-size calculation, codec comparison, mobile-safe playback, color grading, text/caption readability, verification commands, sources.

Related Skills

viral-video-animated-captions - CapCut-style caption generation
viral-video-hook-templates - Hook patterns and retention tactics
ffmpeg-animation-timing-reference - Timing, readability, sync, and platform pacing
ffmpeg-command-syntax - Correct option placement

viral-video-platform-specs