Social media image sizes: dimensions and ratios

What this guide covers

SocialCutter takes one master image and returns a cropped version for each destination. A destination is a platform and format pair: instagram + post, tiktok + cover, youtube + thumbnail.

The API covers 6 platforms, and this is the real response of GET /api/v1/platforms, the same table used by the web dashboard, the REST API and the MCP server. The pixels in the “Size” column are the exact dimensions of the output file, not a suggestion.

Image sizes by platform

Platform	Format	Aspect ratio	Size (pixels)	What it is for
Instagram	post	1:1	1080x1080	Square feed post
Instagram	story	9:16	1080x1920	Story and vertical video
Instagram	landscape	1.91:1	1080x566	Horizontal feed post
Facebook	post	1.91:1	1200x630	Timeline post and link card
Facebook	story	9:16	1080x1920	Vertical story
Facebook	cover	2.63:1	820x312	Page cover
X (Twitter)	post	16:9	1200x675	Image post in the timeline
X (Twitter)	header	3:1	1500x500	Profile header
LinkedIn	post	1.91:1	1200x627	Feed post
LinkedIn	cover	5.9:1	1128x191	Profile or page cover
YouTube	thumbnail	16:9	1280x720	Video thumbnail
YouTube	banner	16:9	2560x1440	Channel banner
TikTok	cover	9:16	1080x1920	Vertical video cover

These are the sizes SocialCutter generates. They are not a copy of the networks’ help pages: they are the real output catalogue of the API, and you can query it yourself at https://api.socialcutter.theboomer.dev/api/v1/platforms. If a network changes its upload requirements, always check its official help center before publishing.

You can print the table from the terminal:

curl -s "https://api.socialcutter.theboomer.dev/api/v1/platforms" | jq

Which size to use for each goal

Goal	Destination	Size and ratio
Square feed post	instagram + post	1080x1080 (1:1)
Story or vertical video	instagram + story, facebook + story	1080x1920 (9:16)
Horizontal timeline post	twitter + post	1200x675 (16:9)
Post with a link card	facebook + post, linkedin + post	1200x630 and 1200x627 (1.91:1)
X profile header	twitter + header	1500x500 (3:1)
LinkedIn cover	linkedin + cover	1128x191 (5.9:1)
YouTube video thumbnail	youtube + thumbnail	1280x720 (16:9)
YouTube channel banner	youtube + banner	2560x1440 (16:9)
TikTok video cover	tiktok + cover	1080x1920 (9:16)
Image for a website or blog	no destination: use the master	Whatever the CMS needs

If the goal is to cover the most slots at the lowest cost, the best pair is 1:1 + 9:16: it covers the square feed and every vertical story and cover for 2 uses.

There is no 4:5 in the catalogue

The 4:5 ratio is widely used in the Instagram feed, but no 4:5 destination exists in the API. There are two honest options:

1. Crop the 4:5 separately. At a width of 1080 pixels, an exact 4:5 measures 1080x1350. No destination produces it: crop it in your editor before or after.
2. contain over instagram + post. The whole image is fitted inside the 1:1 canvas and the gap is filled with background_color, without cropping anything from the original. The resulting file is still a 1080x1080 square: you gain the uncropped image, not a 4:5.

What you will not find is a fit_mode that turns a 1:1 into a 4:5. It does not exist.

Generate every size from a single image

From the web

1. Open the dashboard at https://dash.socialcutter.theboomer.dev.
2. Upload the master image (5 MB maximum) or paste its public URL.
3. Tick the destinations you need from the table above.
4. Pick the fit mode: cover to crop, contain to fit the whole image.
5. Download one image per destination from the history.

From the API: one request, several sizes

curl -s -X POST "https://api.socialcutter.theboomer.dev/api/v1/images/process" \
  -H "X-API-Key: sc_your_key" \
  -H "Content-Type: application/json" \
  -d '{
    "source": { "type": "url", "value": "https://example.com/master.jpg" },
    "destinations": [
      { "platform": "instagram", "format": "post" },
      { "platform": "instagram", "format": "story" },
      { "platform": "linkedin", "format": "post" },
      { "platform": "youtube", "format": "thumbnail" }
    ],
    "options": { "fit_mode": "cover", "format": "webp", "quality": 85 }
  }' | jq

That request costs 4 uses (1 per destination) and returns four URLs, one per destination, each with its platform, format and dimensions. For a local file, upload the binary as multipart:

curl -s -X POST "https://api.socialcutter.theboomer.dev/api/v1/images/process/upload" \
  -H "X-API-Key: sc_your_key" \
  -F "file=@./master.jpg" \
  -F 'destinations=[{"platform":"instagram","format":"post"},{"platform":"tiktok","format":"cover"}]' | jq

From an LLM or agent (MCP)

With the MCP server connected you write no HTTP: ask “process this image for Instagram post, LinkedIn post and TikTok cover” and the model calls the process_image tool with those destinations. The MCP exposes 28 tools over the same API.

Fit modes

fit_mode	What it does
cover	Scales and crops the excess with a centered crop. This is the default.
contain	Fits the whole image and pads the gap with background_color.
fill	Stretches the image to fill the gap; it may distort it.
stretch	Forces the exact dimensions.

None of the four analyses the image content. The cover crop is geometric and centered.

Common mistakes

Mistake	What actually happens	What to do
Uploading a 1:1 image where a 9:16 slot goes	The centered crop drops the top and bottom edges, or the framing is not what you expected	Request the story or cover destination (1080x1920) and check the framing before publishing
Text cut off at the edge	cover crops the excess from the center: whatever touches the edge is lost	Leave a margin around the text in the master, or use contain
Blurry image from upscaling	A small master upscaled to the YouTube banner (2560x1440) loses detail	Start from an original at least 2560 px wide for that destination; never request sizes larger than the master
413 error on upload	The file is over 5 MB	Shrink the master or serve a lighter version over a URL
Expecting it to crop the important part	The image content is not analysed: nothing decides what matters	Frame the subject near the center of the master
Expecting the image to appear published	The API only generates files and returns URLs	Publish through the social network API, your CMS or your automation tool

What SocialCutter does not do

• It is not a photo editor. It does not fix colour or exposure, does not remove backgrounds, does not compose text over the image and does not retouch anything. It produces cropped and scaled versions of the image you give it.
• It does not decide the framing. The crop is centered and deterministic: the image content is not analysed, nothing decides which part matters.
• It does not post to social networks. It returns file URLs. Publishing belongs to the caller.
• It does not accept files over 5 MB on upload.

For retouching, compositing or montage, use a photo editor; for the exact size of each network, use SocialCutter.

Next steps

• Automation: Automating social media images: the 4 real paths
• Terminal: Process images with the API from the terminal (curl)
• LLMs and editors: Use SocialCutter from your LLM or editor with MCP
• No-code: Automate image resizing with n8n
• WordPress: Integrate SocialCutter with WordPress and WooCommerce
• API reference: https://docs.socialcutter.theboomer.dev