The perfect social media post does not exist in the abstract, but the anatomy of a good one is surprisingly consistent. It has a hook that stops the scroll, a visual sized properly for the platform, a caption that is easy to read, one clear call to action, a few relevant hashtags or keywords, alt text, and it goes out when your audience is actually around.

Below we break each part down, in the order we build posts for client accounts, with a table of current sizes and caption limits for Instagram, Facebook, LinkedIn and TikTok. Use it as a checklist before you hit publish.

Start with one clear job for the post

Before writing a word, decide what the post is for. Every post should have one main job:

• Reach: get seen by new people, usually with useful, entertaining or shareable content.
• Engagement: start a conversation, get comments or saves.
• Trust: show your work, your team, reviews or behind the scenes.
• Action: get a click, a booking, an enquiry or a sale.

Posts that try to do all four at once usually do none of them well. The job shapes everything else, from the hook to the call to action.

The hook earns the next second

The hook is the first thing people see: the opening line of the caption, the headline on a graphic, or the first second or two of a video. Its only job is to make someone stop scrolling.

Hooks that work for small businesses tend to be specific and useful rather than clever:

• A clear benefit: “The one thing to check before booking a wedding venue.”
• A number: “3 signs your boiler needs a service before winter.”
• A local angle: “New in Guildford: Saturday morning baking classes.”
• A result you can show: a before and after photo, with the “after” visible straight away.
• A direct question to your audience: used occasionally, not on every post.

For video, put movement or the payoff in the first frame and add on screen text naming the topic. Many people watch with the sound off, so the hook needs to work silently.

The visual does most of the stopping

On every major platform, the image or video is the first thing the eye lands on. A few principles:

• Use real photos where you can. Your team, your premises, your products, your work. They build more trust than stock images.
• One focal point. A clear subject, uncluttered background, good light.
• Minimal text on graphics. A short headline is enough. The detail belongs in the caption.
• Vertical formats take up more of the screen. Portrait images and full screen video generally get more space in the feed than square or wide images.
• Keep important content away from the edges. Profile grids, previews and on screen buttons can crop or cover parts of your image.

Current sizes and limits for 2026

Platforms change their specs regularly, so treat this as a working guide and check the platform’s own help pages if something displays oddly.

Platform	Feed image	Vertical video (Reels, Stories, TikTok)	Caption limit
Instagram	1080 x 1350 pixels (4:5 portrait). The profile grid now shows a taller 3:4 preview, so keep key content central.	1080 x 1920 pixels (9:16)	2,200 characters, maximum 5 hashtags
Facebook	1080 x 1350 pixels (4:5) or 1080 x 1080 (1:1)	1080 x 1920 pixels (9:16)	Very long posts allowed, but only the first few lines show before “See more”
LinkedIn	1200 x 627 (wide), 1080 x 1080 (square) or 1080 x 1350 (portrait)	Vertical video supported, 9:16 or 4:5	3,000 characters for a post
TikTok	Photo posts work best in vertical format	1080 x 1920 pixels (9:16)	4,000 characters

On every platform, only the first line or two of the caption shows before it is cut off, so the opening sentence matters far more than the character limit.

Related reading: How to Create the Perfect Social Media Post (With Infographics)

The caption has a structure

A good caption is easy to skim. We use a simple structure on most posts:

1. Opening line: the hook, or a line that adds to the visual. It needs to make sense even if nobody taps “more”.
2. Value: two to four short sentences or a few short lines giving the useful bit, the story or the detail.
3. Call to action: one clear next step.
4. Hashtags, tags and location: at the end, where relevant.

Write like you talk to customers in person. Short sentences, line breaks between ideas, and the words your customers would use rather than industry terms. An emoji or two can help break up text, but they should not replace words, and screen readers read every one aloud.

Length depends on the job

There is no perfect caption length. A striking product photo might need one line. An educational LinkedIn post might run to several short paragraphs. What matters is that every line earns its place and the first line works on its own.

Finish with one call to action

The call to action, or CTA, is what you want people to do next. Pick one per post and say it plainly:

• “Book your free consultation through the link in our bio.”
• “Save this for your next site visit.”
• “Send us a message with your postcode for a quote.”
• “Tell us in the comments which flavour you want next.”

Remember how each platform handles links. Instagram does not make links in post captions clickable, so point people to your bio link, a DM or a link sticker in Stories. Facebook and LinkedIn allow clickable links in posts. Not every post needs a hard sell. A post designed for reach or trust can simply invite a save, share or comment.

Hashtags, keywords and alt text help people find you

Hashtags are now a supporting act. Platforms work out what a post is about from the caption, on screen text, audio and hashtags together, and plain keywords in your caption increasingly power in app search.

• Instagram: up to five hashtags per post or Reel. A few targeted tags beat lots of generic ones.
• LinkedIn: a small number of relevant hashtags at most. Clear, keyword rich writing matters more.
• TikTok: a few specific hashtags plus keywords in the caption and spoken or on screen text, because TikTok is used heavily as a search engine.
• Facebook: hashtags make little difference for most business pages. Use one only if it is part of a campaign.

Add a location tag where it helps. For local businesses, naming your town in the caption is one of the simplest ways to be found by nearby customers.

Alt text and video captions

Alt text is a short description of an image that screen readers read aloud. Instagram, Facebook and LinkedIn let you add your own when posting, usually under accessibility or advanced settings. Automatic alt text exists but is often vague, so write it yourself:

• Describe what the image shows and why it matters to the post.
• Include any text that is in the graphic.
• Keep it to a sentence or two.

For video, turn on captions. Instagram, Facebook and TikTok all offer automatic captions, but check them for errors before posting, especially names and place names.

Timing and platform fit finish the job

Consistency beats a perfect hour

There is no universal best time to post. It depends on your audience, your sector and the platform. A café’s audience might be most active early morning, a B2B firm’s on weekday lunchtimes. The reliable way to find your times:

1. Check your own insights in Meta Business Suite, LinkedIn page analytics or TikTok analytics, which show when your followers are active.
2. Post at those times for a few weeks and compare results.
3. Adjust based on what you see, not on generic charts.

Consistency matters more than precision. Posting regularly, at a pace you can keep up, does more for an account than finding the perfect minute. And be around after posting: replying to early comments quickly keeps the conversation going.

Platform differences at a glance

• Instagram: visual first. Portrait images, carousels and Reels. Short, punchy captions with keywords. Links via bio or Stories.
• Facebook: community and local. Photos, events, short video and links work well. A conversational tone.
• LinkedIn: professional and text led. Expertise, team news and useful insight. A strong first two lines before “see more”.
• TikTok: video and personality. A fast hook, native editing, trending or original sound, and searchable captions.

Adapt a post for each platform rather than copying the same thing everywhere. The idea can stay the same while the format, length and tone change.

Frequently asked questions

What makes a perfect social media post?

A clear purpose, a strong hook, a well sized visual, a skimmable caption, one call to action, relevant hashtags or keywords, alt text, and posting when your audience is active.

What is the best image size for social media in 2026?

For feed posts, 1080 x 1350 pixels (4:5 portrait) works well on Instagram and Facebook. For Reels, Stories and TikTok, use 1080 x 1920 pixels (9:16).

How long should a social media caption be?

As long as it needs to be and no longer. Make sure the first line works on its own, because that is often all people see.

How many hashtags should I use?

No more than five on Instagram, where that is now the limit, and only a few on other platforms. Relevance matters far more than quantity.

Want posts built like this every week?

Getting every part of a post right takes time, and doing it consistently takes more. Our social media management team plans, writes, designs and schedules content for small businesses, with every post checked against this anatomy before it goes out. Get in touch to talk about your accounts.