Why reference numbers are usually wrong
Cheat sheets copy other cheat sheets. A figure enters circulation once, gets reprinted a hundred times, and by the time you read it the platform changed it two years ago.
Three examples from this section alone. Most size charts still give a YouTube thumbnail as 1280 by 720, while YouTube now recommends 3840 by 2160. Most Instagram hashtag advice still says thirty, while the limit is five. Most Instagram Lite comparisons say it has no Reels, while Meta's own listing says it does.
None of those writers lied. They copied a page that was right once, which is exactly how a reference section rots.
So the rule here is narrow and slow. A number goes on a page only if it was read on the platform's own help page or developer documentation, and the page says when it was read. Where a platform publishes nothing, the page says that too rather than filling the gap with somebody's blog post.
Platforms publish ranges, not numbers
The second reason cheat sheets mislead is that they turn a range into a single figure. Instagram does not say "post at 1080 by 1350". It says it keeps a photo's resolution when the image is 320 to 1080 pixels wide with a ratio between 1.91:1 and 3:4.
That difference matters. The range tells you what happens outside it: narrower images are enlarged, wider ones are reduced, and wrong ratios are cropped to fit. A single recommended size tells you none of that, so the first time something looks wrong you have no way to reason about it.
The same applies to limits that depend on where you are posting from. An Instagram post holds 20 items from the app and 10 through Meta Business Suite. A TikTok video can be trimmed in the app and not on the web. A YouTube thumbnail can weigh 2MB from a phone and 50MB from a computer.
Whenever a number surprises you, the usual explanation is that you are on a different surface than the person who wrote it down.
Some limits are not counted the way you think
X is the clearest case. A post holds 280 characters, and the characters are weighted. Latin letters and punctuation count as one. Emoji count as two, whatever their complexity, so 140 emoji fill a post. Chinese, Japanese and Korean characters also count as two.
Then the parts that cost nothing or a fixed amount. Any link counts as 23 characters regardless of its real length, so shortening a URL yourself saves nothing. Attached media costs zero. The names automatically added at the start of a reply cost zero, while a mention you type yourself counts normally.
That single set of rules changes how a post is written. A post with a link and a photo has 257 characters of room, not 280 minus the length of the URL.
Timing is where the numbers are weakest
No platform publishes a best time to post. Every table in circulation comes from a scheduling company measuring its own customers, and those samples disagree with each other on the biggest questions.
On TikTok, one study names Sunday as the single best slot of the week, another calls Sunday the absolute peak, and a third says avoid the weekend entirely. On Facebook, one study's prime window is another study's worst block of the day.
Only one study read for this section publishes the size of the effect rather than a ranking. Across 40.2 million uploads, the best day beat a channel's own average by about 3.5% and the worst trailed by about 2.2%, and the exact upload hour barely moved views by day 30.
Keep that number in mind whenever someone sells you a posting schedule. A ranking looks the same whether the gap is forty percent or two.
How to use a reference page without being caught out
- Check the date it was read. Every page in this section carries one. A reference page without a date is a guess with formatting.
- Check the surface. App or web, personal or business account, and which country. Most contradictions dissolve here.
- Prefer the range to the recommendation. Knowing what happens outside the limit tells you more than the ideal number.
- Treat undocumented behavior as undocumented. If a platform never published it, no article can turn it into a rule.
- Re-check anything you are about to print. Packaging, templates and brand kits outlive platform specifications.
The numbers, on one screen
These are the figures this section actually stands behind. Each row links to the guide that names the help page it came from, so you can check any of them without taking our word for it.
Text and captions
Video and story length
Sizes and files
Posting and scheduling
What is not in these tables matters as much as what is. There is no daily posting limit for Instagram or TikTok, no hourly like or comment cap, and no published duration for a temporary block. Those numbers exist on dozens of pages and on none of the platforms' own.
Aspect ratios, pixels and the safe area
Most size questions are really ratio questions. A platform crops by shape first and resamples by pixels second, so an image in the right ratio at the wrong resolution survives, and an image at the right resolution in the wrong ratio does not.
The safe area is the part no cheat sheet prints. On a vertical video the top and bottom of the screen carry the profile row, the caption, the buttons and the reply bar, so anything that has to be read belongs in the middle two thirds of the frame. An image sized perfectly and composed to the edges still loses its text.
The full working set, including how to export so the platform does not resample your images twice, is in the post size guide.