| Spec | What the platform documents |
|---|---|
| max caption/post character limit | not officially documentedGraph API Page feed 'message' param is defined only as 'The main body of the post' with no character limit stated. No consumer Help Center page stating a post character limit was found. The commonly-recalled 63,206 does not appear in official docs. developers.facebook.com — checked 6 August 2026 |
| recommended image aspect ratio | not officially documented (organic)Aspect-ratio guidance exists only in Meta Ads Manager docs; no organic aspect ratio stated on fetched pages. developers.facebook.com — checked 6 August 2026 |
| image max file size | 10MB (PNG recommended <=1MB to avoid pixelation); formats .jpeg, .bmp, .png, .gif, .tiffExact text: 'Files can not exceed 10MB. For .png files, we recommend not exceeding 1MB or the image may appear pixelated.' developers.facebook.com — checked 6 August 2026 |
| max video length (feed + short-form) | No fixed limit stated: 'All videos posted to Facebook are now shared as reels... Reels can be any length or orientation' (change effective June 2025)Reels recommended specs on same page: .mp4, 1080p, H.264/H.265, 24-60 FPS. A 241-minute max exists only for the Facebook Feed AD placement (Ads Manager page 817989058548892), excluded per organic-only rule. www.facebook.com — checked 6 August 2026 |
| max video file size | not officially documented (organic)Neither the Reels requirements page nor the Video API docs state an organic file-size cap. www.facebook.com — checked 6 August 2026 |
| hashtag limit | not officially documented www.facebook.com — checked 6 August 2026 |
| link behavior | Links attachable to posts and render as a link attachment with scraped preview: 'The URL of a link to attach to the post. Either link or message must be supplied.' developers.facebook.com — checked 6 August 2026 |
Reference
Social media post size limits and specs
Caption ceilings, image and video caps, hashtags and links for nine channels — every figure read off the platform's own documentation and dated.
Every figure checked 6 August 2026.
Nine channels publish out of this product, so these are not trivia to us. A caption ceiling is what our own uploader has to respect before it hands a post to Meta or LinkedIn or TikTok, and a file cap is what decides whether a rendered video arrives or bounces. Keeping the numbers true is maintenance we already owe, which is the only sound reason to publish a reference page rather than borrow one.
Each figure below was read off the platform's own documentation and carries a link to the page it came from, beside the date it was read. Nothing here comes from a roundup, an agency blog, or a number that simply gets repeated. That restraint is visible in the tables: where a platform documents nothing, the row says so, and 14 of the 55 rows say exactly that.
Those gaps are the finding, not a shortfall. Facebook states no organic caption limit anywhere in its own docs, and the 63,206 characters everyone quotes appears in none of them. Google Business Profile's much-cited 1,500-character cap lives in a community thread rather than a help article. Both are recorded here as undocumented, because the alternative is to launder a rumour into a citation.
How these numbers were checked
- Primary sources only
- Every value came from the platform's own developer reference or help centre, fetched on the date each row carries. Where the documentation quotes itself usefully, the quotation is reproduced rather than paraphrased, so you can match our wording against theirs without opening the tab.
- Two official answers get two answers
- Instagram's help centre caps hashtags at five; Instagram's own publishing API reference allows thirty in a caption. Both were live on the same day. We publish the conflict instead of resolving it for you, because a page that quietly picks a side is asserting a consensus that does not exist.
- Organic posting, not ad placements
- Ads Manager documents its own numbers, and they differ. The 241-minute video length attached to Facebook everywhere is the feed ad placement, not an organic post, so it is excluded. Every row here describes what an ordinary published post has to satisfy.
- A gap stays a gap
- 14 rows read as undocumented. Filling one of them from a third-party figure would make the whole table unciteable, because you would have no way of telling which cells were verified and which were remembered. An empty cell you can trust beats a full one you cannot.
Limits by platform
One table per channel. Jump straight to the one you need:
| Spec | What the platform documents |
|---|---|
| max caption/post character limit | 2,200 characters maximum (caption may also include max 30 hashtags and 20 @ tags)Exact text: 'Maximum 2200 characters, 30 hashtags, and 20 @ tags.' From the IG User Media (content publishing) API reference — the surface SpeedRun publishes through. developers.facebook.com — checked 6 August 2026 |
| recommended image aspect ratio + max file size | Aspect ratio must be within 4:5 to 1.91:1; JPEG only; 8MB max; width 320-1440px developers.facebook.com — checked 6 August 2026 |
| max video length (feed/Reels + Stories) | Reels (all feed video): 15 minutes max, 3 seconds min. Story video: 60 seconds maxRecommended aspect ratio 9:16; max 1920 horizontal pixels; MOV/MP4, H.264/HEVC, 23-60 FPS. developers.facebook.com — checked 6 August 2026 |
| max video file size | Reels: 300MB maximum. Story video: 100MB maximum developers.facebook.com — checked 6 August 2026 |
| hashtag limit | CONFLICTING OFFICIAL DOCS: Help Center says 'You can use up to 5 tags on a post. If you include more than 5 tags on a single photo/video, your comment won't post.' API reference says caption maximum '30 hashtags'API source for the 30 figure: https://developers.facebook.com/docs/instagram-platform/instagram-graph-api/reference/ig-user/media. Both fetched 2026-08-06. Since SpeedRun publishes via the API, 30 is the enforced API cap, but the consumer help page now says 5 — surface both, do not silently pick one. help.instagram.com — checked 6 August 2026 |
| link behavior | not officially documentedCaption help page does not address link clickability; no fetched official page states whether caption URLs are clickable. Story link stickers are explicitly NOT supported via the publishing API ('Publishing stickers (i.e., link, poll, location) is not supported'). help.instagram.com — checked 6 August 2026 |
| Spec | What the platform documents |
|---|---|
| max caption/post character limit | 3,000 characters ('The character limit for a post is 3,000 characters'); articles 'are limited to 125,000 characters'Article figure from https://www.linkedin.com/help/linkedin/answer/a522483 ('Articles are typically longer than posts and are limited to 125,000 characters'), fetched 2026-08-06. The post-limit page itself names no article figure — it only says a post over 3,000 characters can be written as an article instead. www.linkedin.com — checked 6 August 2026 |
| recommended image aspect ratio + max file size | Aspect ratio 3:1 to 4:5 (width:height); 5MB max per upload; min 552x276px, recommended 1080px wide; up to 20 photos per multi-photo post www.linkedin.com — checked 6 August 2026 |
| max video length | 15 minutes maximum (min 3 seconds desktop / 2 seconds mobile) www.linkedin.com — checked 6 August 2026 |
| max video file size | 5GB maximum (75KB minimum); aspect ratio 1:2.4-2.4:1; resolution 256x144 to 4096x2304 www.linkedin.com — checked 6 August 2026 |
| hashtag limit | not officially documentedNo LinkedIn Help page stating a hashtag cap was found. Pages searched: posts (a528176), photos (a527229), videos (a548372) and posts-vs-articles (a522483) — none names a hashtag limit. www.linkedin.com — checked 6 August 2026 |
| link behavior | not officially documentedFetched help pages (a528176, a527229, a548372, a522483) do not describe organic link/preview behavior. www.linkedin.com — checked 6 August 2026 |
X
| Spec | What the platform documents |
|---|---|
| max caption/post character limit | 280 characters ('Type your post (up to 280 characters)'); X Premium longer posts up to 25,000 characters help.x.com — checked 6 August 2026 |
| recommended image aspect ratio + max file size | Photos up to 5MB; animated GIFs up to 5MB mobile / 15MB web; GIF, JPEG, PNG only; 1-4 photos per post. Aspect ratio: not officially documented for photos help.x.com — checked 6 August 2026 |
| max video length | 140 seconds (non-Premium); Premium: 'videos shorter than 4 hours at 1080p'Web upload constraints on same page: aspect ratio 1:2.39-2.39:1 inclusive, max resolution 1920x1200 (and 1200x1900), max 40 fps, max 25 Mbps. help.x.com — checked 6 August 2026 |
| max video file size | 512MB (non-Premium); Premium: 16GB maximum help.x.com — checked 6 August 2026 |
| hashtag limit | No hard limit: 'We recommend using no more than 2 hashtags per post as best practice, but you may use as many hashtags in a post as you like.' help.x.com — checked 6 August 2026 |
| link behavior | Links allowed directly in posts: 'A post may contain photos, GIFs, videos, links, and text.'URL character-counting rules (t.co) live on developer.x.com which returned HTTP 402 — not verified, so not recorded. help.x.com — checked 6 August 2026 |
TikTok
| Spec | What the platform documents |
|---|---|
| max caption/post character limit | 2,200 UTF-16 runes (video 'title'/caption field via Content Posting API)Hashtags (#) and mentions (@) are parsed within the caption. developers.tiktok.com — checked 6 August 2026 |
| recommended image aspect ratio + max file size (photo posts) | Max 20MB per image; WebP/JPEG; picture size maximum 1080p. Aspect ratio: not officially documented developers.tiktok.com — checked 6 August 2026 |
| max video length | 'All TikTok creators can post 3-minute videos, while some have access to post 5-minute or 10-minute videos. The longest video a developer can send via the initialize Upload Video endpoint is 10 minutes.' developers.tiktok.com — checked 6 August 2026 |
| max video file size | 4GB maximum; MP4 (recommended), WebM, MOV; H.264 recommended; 23-60 FPS; 360-4096px each dimension developers.tiktok.com — checked 6 August 2026 |
| hashtag limit | not officially documented (no separate cap; hashtags count within the 2,200-rune caption) developers.tiktok.com — checked 6 August 2026 |
| link behavior | not officially documentedFetched official docs do not state whether caption URLs are clickable. developers.tiktok.com — checked 6 August 2026 |
YouTube (Shorts)
| Spec | What the platform documents |
|---|---|
| max caption/post character limit | Description: 'maximum of 5000 characters'. Title limit: not verified on a fetched official pageThe widely-cited 100-character title limit did not appear on any page fetched — deliberately omitted rather than recalled. support.google.com — checked 6 August 2026 |
| recommended image aspect ratio + max file size (thumbnail) | Thumbnail: 16:9 recommended (Shorts thumbnail 9:16, 2160x3840); resolution 3840x2160 (min width 640px); 2MB mobile / 50MB desktop; JPG, GIF, PNGYouTube has no organic feed-image concept; thumbnail is the image spec. support.google.com — checked 6 August 2026 |
| max video length (feed + Shorts) | Regular uploads: 12 hours max (verified accounts; default 15 minutes). Shorts: up to 3 minutes, vertical, max resolution 1080pShorts figures from https://support.google.com/youtube/answer/10059070 (also checked 2026-08-06). No explicit 9:16 ratio stated — page says 'vertical' only. support.google.com — checked 6 August 2026 |
| max video file size | 'The maximum file size you can upload is 256 GB or 12 hours, whichever is less.' support.google.com — checked 6 August 2026 |
| hashtag limit | 'If a video or playlist has more than 60 hashtags, we'll ignore each hashtag on that content.' Display: 'Out of all the hashtags you add to the video's description, up to three hashtags that are considered most engaging will appear by your video title.'Both sentences are verbatim from the same page. An earlier draft paraphrased the display behaviour as 'first 3 shown above the title'; the paraphrase was replaced with the page's exact wording — YouTube picks the three 'considered most engaging', not the first three. support.google.com — checked 6 August 2026 |
| link behavior | not officially documentedFetched pages do not state description-link clickability rules. support.google.com — checked 6 August 2026 |
| Spec | What the platform documents |
|---|---|
| max caption/post character limit | Title: 100 characters max. Description: up to 800 characters (not shown in feed view; used by the relevance algorithm). Textbox: 250 characters maxFrom Pinterest's organic Review Pin specs page. Feed truncation is documented only on the ad-spec page (https://help.pinterest.com/en/business/article/pinterest-product-specs), where standard image ads state 'Depending on the device, the first 40 characters may show in people's feeds' — an ad-format figure, not an organic spec. help.pinterest.com — checked 6 August 2026 |
| recommended image aspect ratio + max file size | Max file size: 20MB (web) / 1GB recommended (Android and iOS); file types .BMP, .JPEG, .PNG, .TIFF, .WEBP. Aspect ratio: not officially documented for organic image PinsThe 2:3 (1000x1500px) recommendation, 20MB desktop / 32MB in-app caps and PNG/JPEG-only list are Pinterest's ad-format specs, excluded per the organic-only rule. The organic page gives image Pins safe zones rather than an aspect ratio. help.pinterest.com — checked 6 August 2026 |
| max video length | 'Minimum 4 seconds, maximum 5 minutes'; recommended 9:16 (or 1080x1920) for full-bleed video, with 1:2, 2:3, 3:4, 4:5 and 1:1 as other optionsThe 15-minute maximum previously shown here is Pinterest's AD video spec; the organic Review Pin specs page states a 5-minute maximum. help.pinterest.com — checked 6 August 2026 |
| max video file size | not officially documented for organic PinsThe organic Review Pin specs page states video file types (.MP4/.M4V on web; .MP4/.MOV/.M4V on Android and iOS) and H.264/H.265 encoding, but no maximum video file size. The 2GB cap previously shown here is the ad-format spec, excluded per the organic-only rule. help.pinterest.com — checked 6 August 2026 |
| hashtag limit | not officially documentedNeither the organic Review Pin specs page nor the create-a-Pin page (https://help.pinterest.com/en/article/create-a-pin-from-an-image-or-video) states a hashtag cap; the create-a-Pin flow only notes a description 'can also include hashtags'. help.pinterest.com — checked 6 August 2026 |
| link behavior | Pins carry a dedicated destination-link field: 'add a link to give people on Pinterest a place to learn more' (optional, for both image and video Pins) help.pinterest.com — checked 6 August 2026 |
Google Business Profile
| Spec | What the platform documents |
|---|---|
| max caption/post character limit | not officially documentedThe commonly-cited 1,500-character limit appears only in a community thread, not in the official help articles fetched (7342169, 7390603, 7662907). Official page also warns: 'Posts that include a phone number in the post description might get rejected.' support.google.com — checked 6 August 2026 |
| recommended image aspect ratio + max file size | JPG or PNG; between 10KB and 5MB; recommended resolution 720x720px; minimum 250x250px. Aspect ratio: not stated beyond square recommendation support.google.com — checked 6 August 2026 |
| max video length | Up to 30 seconds; resolution 720p or higher support.google.com — checked 6 August 2026 |
| max video file size | Up to 75MB support.google.com — checked 6 August 2026 |
| hashtag limit | not officially documented (hashtags are not a documented GBP post feature) support.google.com — checked 6 August 2026 |
| link behavior | Posts support 'an action button with a link' (Updates/Events); Offers additionally support a link and coupon code field support.google.com — checked 6 August 2026 |
Mailchimp (email)
| Spec | What the platform documents |
|---|---|
| max caption/post character limit | Not applicable — no email body character limit documented. Subject line official recommendation: 'we recommend you use no more than 9 words and 60 characters' (recommendation, not a hard limit) mailchimp.com — checked 6 August 2026 |
| recommended image aspect ratio + max file size | 'We recommend a maximum file size of 1MB for images'; PNG, JPG, or GIF; new builder image width 660-1320px (legacy 600-1200px). Content studio upload limits: images up to 1MB each, other files up to 10MB each. Aspect ratio: not officially documentedContent studio limits from https://mailchimp.com/help/use-the-content-studio/ (also checked 2026-08-06). mailchimp.com — checked 6 August 2026 |
| max video length | Not applicable — video cannot be embedded: 'Most email clients can't display embedded video content, and will strip the code from your email.' Use video content blocks / merge tags that render a linked thumbnail mailchimp.com — checked 6 August 2026 |
| max video file size | Not applicable (no direct video embedding; video is shared as a linked thumbnail to an external host) mailchimp.com — checked 6 August 2026 |
| hashtag limit | Not applicable (email has no hashtag concept; not documented) mailchimp.com — checked 6 August 2026 |
| link behavior | Links are standard clickable email hyperlinks; for video, 'The Video content block adds a play icon on the thumbnail image from your Vimeo or YouTube video. When recipients click the thumbnail, the video will open in a new browser window.' mailchimp.com — checked 6 August 2026 |
Change log
A value is edited only after its source page has been read again. When that happens, the row's date moves and a line lands here.
- 2026-08-06: initial publication. Nine platforms, every row read off the platform's own developer reference or help centre on that date, with the source link and the check date shipped beside each value.
- 2026-08-06: corrected LinkedIn caption row — the 125,000-character article limit was not on the cited post-limit page; it is now quoted from LinkedIn's posts-vs-articles help page (a522483), which states it verbatim.
- 2026-08-06: corrected YouTube hashtag row — replaced the paraphrase 'up to 3 shown above the title' with the page's exact wording: up to three hashtags 'considered most engaging' appear by the video title.
- 2026-08-06: corrected Pinterest caption row — re-sourced from the ad-spec page to the organic Review Pin specs page, and replaced the '~40 shown' hedge with the ad page's exact 40-character feed-truncation sentence, marked as ad-format.
- 2026-08-06: corrected Pinterest image row — the 2:3 (1000x1500px) recommendation and 20MB/32MB caps were ad-format specs; the organic page states 20MB on web, 1GB recommended in-app, five file types and no aspect ratio.
- 2026-08-06: corrected Pinterest video length row — 15 minutes was the ad-format maximum; the organic page states a 5-minute maximum.
- 2026-08-06: corrected Pinterest video file size row — the 2GB cap was ad-format; the organic page states no maximum, so the row now reads as undocumented.
- 2026-08-06: corrected Pinterest hashtag row — now cites the organic Review Pin specs page rather than the ad-spec page; still no documented cap.
- 2026-08-06: corrected Mailchimp link row — the video-thumbnail description was a paraphrase presented as a quotation; it now reproduces the help page's sentences verbatim.
Questions these tables raise
How long can a caption be on each platform?
Documented ceilings: Instagram 2,200 characters, TikTok 2,200 UTF-16 runes, LinkedIn 3,000, X 280 (25,000 with Premium), a YouTube description 5,000, and a Pinterest title 100 with an 800-character description. Facebook and Google Business Profile publish no organic caption limit at all in the pages checked, which is why both rows read as undocumented rather than carrying the figures usually quoted for them.
How many hashtags can you use on an Instagram post?
Instagram's own documentation gives two different answers. The consumer help centre says five tags on a post, and says a comment carrying more than five will not post. The publishing API reference says a caption may contain 2,200 characters, 30 hashtags and 20 @ tags. Both were live on 6 August 2026. Anything publishing through the API meets the API's limit; anything typed into the app meets the app's. Treat five as the safe number if you want one rule that holds everywhere.
Why do some rows say the limit is not officially documented?
Because the platform does not state one on any page we could read. 14 rows land there, including Facebook's caption limit, LinkedIn's hashtag cap and link behaviour on four different networks. Every widely-published number for those cells traces back to somebody's inference rather than to the platform, and reprinting an inference as a specification is how a reference page stops being one.
Do these limits apply to paid ads as well as ordinary posts?
No. Ad placements are documented separately and their numbers differ, sometimes dramatically — the 241-minute Facebook video length is a feed ad specification, not something an organic post can use. Everything on this page describes organic publishing, which is what a scheduling or generation tool actually submits.
How current is this, and what happens when a platform changes?
Every row carries the date it was verified, and the change log records what moved and when. A value is only edited after its source page has been read again, so the date beside a number is a claim about that specific check rather than about the page as a whole. If a figure here disagrees with what a platform tells you, follow the source link — it is the same page we read.
Let the tool keep track of the limits
SpeedRun Social writes each caption to the channel it is going to and renders media inside these caps. A free account includes one campaign a week, every week, which comes to 12 posts, 4 videos and 4 cross-posts a month, plus 300 credits refilled monthly and no credit card.