Merchants keep resizing the same clip for four platforms on guesswork, and the only numbers that can actually be checked right now come from postal rate documentation rather than any social platform, which settles far less than most guides pretend to settle.
Most merchants searching for social video sizes expect a clean table of pixel dimensions for Instagram, TikTok, Pinterest, and YouTube, and assume any article carrying that title has one. That assumption is wrong here, and it is worth saying so directly instead of padding the page with numbers pulled from memory. The only facts verified for this piece, checked on September 30, 2026, come from USPS Notice 123, a postal rate document that lists percentage discount tiers for mailed publications. It does not mention aspect ratio, resolution, or maximum upload duration for any video platform. Rather than dress up guessed numbers as measured ones, this article reports exactly what was checked and leaves the rest open.
USPS Notice 123 lists three figures relevant to this check: a single issue purchase tier at 90%, an authorized publications discount at 5%, and a nonadvertising adjustment factor of 1% applied to each qualifying item. These numbers were read from the Notice 123 tables as loaded on September 30, 2026. They describe how postal rates are discounted for certain classes of printed mail. None of them describe a video file, a frame rate, or a platform upload limit, and treating them as if they did would break the one rule this site follows: every number in the text must trace to a measured fact, and no fact here measured a social platform.
The same three figures, 5%, 1%, and 90%, appear twice in the source material supplied for this check, once as a general table row and once repeated under the same labels. That repetition does not create new information. It confirms the same tier structure was recorded consistently across the document as of the September 30, 2026 read, which is useful for verifying the postal document itself but adds nothing toward an Instagram, TikTok, Pinterest, or YouTube dimension.
| Tier label | Value |
|---|---|
| Authorized publications receive | 5% |
| Nonadvertising adjustment factor for each | 1% |
| A single issue can be purchased for | 90% |
A trustworthy spec sheet for Instagram, TikTok, Pinterest, or YouTube needs pixel width and height, maximum file size, maximum duration, and a checked date for each platform separately, because platforms change these values without notice. None of those figures were part of the fact set supplied for this review. Filling them in from memory would satisfy the reader’s immediate question but would break the single rule that governs this site, which is that every digit printed must come from a document someone actually opened and dated. The gap here is real and stated as measured, not softened into a maybe.
A merchant who needs exact dimensions right now should open each platform’s current help center page directly and note the date read, the same discipline applied to the USPS document in this piece. Until that per-platform check happens, this article can only confirm what it verified: three postal percentage tiers, 5%, 1%, and 90%, checked September 30, 2026, and nothing about video pixels at all.
This article cannot state that number. The only facts verified for this piece come from USPS Notice 123, a postal rate document, and it contains percentage tiers like 5%, 1%, and 90%, not pixel dimensions. A merchant needs a platform-specific spec sheet checked on its own date to get an accurate Reels size, and this review does not have that document in hand.
Because the only measured facts supplied for this piece came from USPS Notice 123, checked September 30, 2026, and the rule this site follows is that every number printed must trace back to a verified fact. Rather than invent Instagram or TikTok dimensions from memory, the article states plainly that those numbers were not available and shows what was actually measured instead.
No. Those percentages describe postal tiers, specifically a single issue purchase tier at 90%, an authorized publications tier at 5%, and a nonadvertising adjustment factor of 1%, all pulled from USPS Notice 123. They have no connection to video compression, aspect ratio, or file size limits on any social platform, and applying them there would be a fabrication.
Go to each platform's own current help documentation and note the date you read it, the same way this piece notes September 30, 2026 for its postal source. A spec sheet without a checked date is not reliable because platforms revise upload requirements without announcing it, so the date functions like a version number.