video-spec-sheet

Overview

Each social platform has its own combination of aspect ratio, max duration, codec, bitrate, frame rate, and caption / UI safe zones. Getting any of these wrong on the export means the platform will either reject, re-encode (quality drop), or crop your creative. This skill encodes the 2026 specs as a single table the agent extracts from per brief. Caps and safe zones move several times a year: treat every number marked 2026 as a starting point and confirm it against the platform's live spec page before a paid launch.

Instructions

Core Rules

• Always pick the platform spec before generating frames — generation must match the export aspect ratio (don't generate 16:9 then crop to 9:16 unless intentional).
• Burn captions on top of the base render, not as a sidecar. Don't assume Reels are watched sound-off: Meta reports over 75% of Reels views are sound-on (official, Meta for Developers, 2024-11-07). Captions carry the message for the muted viewer and accessibility while the audio carries it for everyone else; in TikTok's Kantar survey 88% of TikTok users said sound is essential (self-reported; official, TikTok for Business blog, 2021-06). Render them from word timings through libass with the video-captions skill; stock Homebrew ffmpeg has no libass.
• Respect the safe zone — keep all critical text and faces away from where the platform's UI sits (top, bottom, right side for TikTok).
• Final encode in H.264 / yuv420p, even if the source is HEVC / 10-bit. Universal compatibility beats marginal quality.
• Audio: AAC-LC stereo, 48 kHz, 128 kbps minimum (YouTube recommends 384 kbps stereo for uploads). Mono audio reads as low-quality on most feeds.
• Loudness: master to about -14 LUFS integrated, true peak ≤ -1 dBTP. YouTube normalizes to roughly that level; TikTok and Meta don't publish a target, so -14 is a safe common master.
• AI-generated clips usually come out at 720p (Runway Gen-4 Turbo renders 1280×720 / 720×1280). Upscale picked shots before the final 1080p encode; never let the platform upscale.
• Re-encoding with ffmpeg drops any C2PA Content Credentials the generator embedded, so platform auto-labelling of AI content will not fire. Disclose manually at upload (see Disclosure and Rights).

Platform Spec Table (2026 — verify live)

Safe Zones (keep critical text, faces and logos out of these UI bands)

(Pixels at 1080×1920 or 1920×1080; scale with output resolution. Ads that carry a legal disclaimer on Meta need the bottom 40% clear.) Instagram's profile grid crops covers to 3:4, so keep the cover's subject and title inside the centre 1080×1440.

Captions / On-Screen Text Rules

• Keep the caption block out of every UI band; never bottom-aligned (bottom is platform UI).
• 9:16 talking head: block centered at about 58% of height (Y≈1110 of 1920), just below the chin and above the bottom band. Never over the face.
• 9:16 product or screen demo with the subject mid-frame: upper third (about 30% of height), still below the top band.
• Font: bold sans (Poppins Black, Montserrat Black, Anton, Inter Black). Caption text roughly 80–110 px at 1080×1920, hook text slightly smaller in a box.
• Stroke + drop shadow: about 8% of font size stroke, soft shadow — preserves readability over any background.
• One sentence per card max. Two-sentence cards get skipped.
• Word-by-word reveal in time with VO is the common preset look; test it against flat full-sentence captions on the account's own data (no measured source). Keep on-screen text at or under 5–10 words per second (TikTok creative guidance).
• Instagram captions hold at most 2,200 characters (official, Meta developer docs, Instagram Graph API media reference). Instagram posts allow at most 5 hashtags (reported, Business Today, 2025-12-19; newer than the API reference, which may lag). Put the hook and topic words in the first line, before the "more" truncation.

Output Presets (ffmpeg) — copy-paste ready

# 9:16 — TikTok / Reels / Shorts / Stories
-vf "scale=1080:1920:force_original_aspect_ratio=decrease,pad=1080:1920:(ow-iw)/2:(oh-ih)/2:color=black,fps=30" \
  -c:v libx264 -profile:v high -level 4.0 -crf 21 -preset slow -pix_fmt yuv420p \
  -c:a aac -b:a 128k -ar 48000 -ac 2 \
  -movflags +faststart

# 1:1 — IG / FB feed
-vf "scale=1080:1080:force_original_aspect_ratio=decrease,pad=1080:1080:(ow-iw)/2:(oh-ih)/2:color=black,fps=30" \
  -c:v libx264 -profile:v high -crf 21 -preset slow -pix_fmt yuv420p \
  -c:a aac -b:a 128k -ar 48000 -ac 2 -movflags +faststart

# 16:9 — YouTube long-form / LinkedIn
-vf "scale=1920:1080:force_original_aspect_ratio=decrease,pad=1920:1080:(ow-iw)/2:(oh-ih)/2:color=black,fps=30" \
  -c:v libx264 -profile:v high -level 4.2 -crf 19 -preset slow -pix_fmt yuv420p \
  -c:a aac -b:a 192k -ar 48000 -ac 2 -movflags +faststart

Workflow

1. Identify primary platform for the brief (TikTok / Reels / Shorts / etc.).
2. Pick aspect, length cap, fps from the table.
3. Mark safe zones when storyboarding — keep face, hook text, CTA inside the center region.
4. At export, use the matching ffmpeg preset above.
5. If publishing to multiple platforms, render the master in the largest aspect (e.g. 9:16 1080×1920 30fps) and downconvert to others — never upscale.

Decision Guide

Disclosure and Rights (2026 — verify live)

Examples

Example 1: TikTok ad export

Source: 4K 16:9 24fps generated at Veo. Target: TikTok ad.

ffmpeg -i source.mp4 \
  -vf "scale=1080:1920:force_original_aspect_ratio=decrease,pad=1080:1920:(ow-iw)/2:(oh-ih)/2:color=black,fps=30" \
  -c:v libx264 -profile:v high -level 4.0 -crf 21 -preset slow -pix_fmt yuv420p \
  -c:a aac -b:a 128k -ar 48000 -ac 2 \
  -movflags +faststart \
  tiktok-ad-9x16.mp4

Example 2: Cross-platform render plan

Brief: One ad, ship to TikTok + IG Reels + IG feed + YT Shorts + YT long-form trailer.

Checklist

• Aspect and resolution match the platform row; no platform-side upscaling.
• Length is under the 2026 cap and the cap was checked live for paid launches.
• Captions, faces and CTA sit outside every UI band of every placement the cut will run in.
• H.264 yuv420p, AAC 48 kHz stereo, +faststart, about -14 LUFS / -1 dBTP.
• AI-disclosure and music-rights rows resolved for each platform.

References

• TikTok in-feed ad specs
• TikTok ad disclaimers (AI-generated content)
• Instagram Reels ad specs and safe zones
• YouTube Shorts up to 3 minutes
• YouTube recommended upload encoding settings
• YouTube altered or synthetic content disclosure
• Meta Ads Guide
• New York synthetic performer ad disclosure, GBL § 396-b (Cooley summary)
• TikTok creative best practices
• Instagram Reels length (Instagram Help via Socialinsider), 2026-07, reported.
• Meta Reels ads, sound-on share, 2024-11-07, official.
• Instagram five-hashtag cap (Business Today), 2025-12-19, reported.
• Instagram Graph API: IG User media, official — caption maximum 2,200 characters.
• TikTok for Business: Kantar report on sound, 2021-06, official — 88% of TikTok users say sound is essential (self-reported).