Social Media Image Size Checker

What the checker measures

Four properties are read straight from the file, then compared against each placement specification:

• Pixel dimensions — the image's true width and height, not the size it was displayed at in a design tool.
• Aspect ratio — reduced to its simplest form and snapped to a familiar name when it is within about 1% of a common ratio, so 1079x1080 reads as 1:1 rather than a fraction nobody recognises.
• Format — JPEG, PNG, WebP or GIF.
• File size — checked against per-placement caps where the platform enforces one.

The verdicts are deliberately blunt. A placement fails when the aspect ratio falls outside its tolerance, because the platform will crop rather than letterbox, or when the width is under that placement's hard minimum. It warns when the ratio is right but the width falls short of the recommended figure, which produces a soft image on high-density screens, or when the file exceeds a size limit.

Why aspect ratio matters more than resolution

Resolution problems are gradual: an image 20% below the recommended width looks slightly soft. Ratio problems are binary — the platform crops to its own frame and something disappears.

Take a 1920x1080 hero image pushed to an Instagram Story. The Story frame is 9:16. To fill it, the platform either strands the image in a strip in the middle of the screen or scales it up and cuts the sides off entirely, and the sides are where the logo and the offer usually sit. No amount of extra resolution repairs that; only re-cropping does.

This is also why exporting one master asset for everything fails. A 1:1 square and a 9:16 vertical are not two sizes of the same image, they are two compositions. Practical mitigations:

• Design the vertical version first. Cropping down from 9:16 to 4:5 or 1:1 is far easier than inventing top and bottom space that was never shot.
• Keep type and logos inside a central safe area, clear of the outer 10 to 15% on every edge, because that band is what different frames eat first.
• Never let a headline sit against the very top or bottom of a Story — platform UI, captions and the profile row overlay those strips.
• Check legibility at thumbnail scale. A YouTube thumbnail is often seen around 210px wide in a sidebar, where six words of small type in the master file are unreadable.

Social media image sizes by platform

These are the exact specifications the checker tests against. Where a placement carries a file size cap, it appears in the notes.

Instagram image sizes

4:5 portrait is the highest-value feed format because it occupies more screen height than a square at the same scroll position. The trade-off is that the same file will not work as a square without a re-crop.

Facebook image sizes

LinkedIn image sizes

That 5.9:1 company cover is the most common failure in this list. Almost nothing crops into a band that shallow gracefully, so it needs artwork built for the ratio rather than a resized photograph.

X (Twitter) image sizes

TikTok image sizes

A cover frame does double duty: full-screen while the video loads, and a small tile cropped towards the centre in your profile grid. Text near the edges reads fine in one context and is amputated in the other.

YouTube image sizes

The 2 MB thumbnail cap catches people out constantly, because a detailed 1280x720 PNG export can pass it easily while the same image as a quality-85 JPEG lands around a tenth of the size.

Pinterest image sizes

How platform compression works, and how to survive it

Every platform re-encodes what you upload. They are serving billions of images over metered mobile connections, so they downscale to their own display widths, strip metadata, and re-compress with settings tuned for bandwidth rather than for your gradient.

The damage is not evenly distributed. Photographs with natural texture hide compression artefacts well. Flat colour, smooth gradients, fine type and hard edges are where banding and edge noise become obvious — which is exactly what most brand and promotional assets are made of.

You cannot switch the compression off, but you can stop compounding it:

• Upload at the recommended dimensions rather than far above them. A 4000px-wide file gets downscaled by the platform's own resampler, which is usually less careful than yours.
• Never re-upload an image that has already been through a platform. Downloading a post and reposting it stacks a second generation of lossy encoding on the first.
• Export once from the master. Every intermediate JPEG save is another generation of loss.
• Avoid hairline type and 1px rules. Anything under roughly 2px at final size is a candidate for being smeared.
• Add a little noise to large flat gradients. It costs a small amount of file size and largely prevents visible banding.
• Sharpen after resizing, not before, and only mildly — over-sharpened edges give the encoder something to ring around.

File size and format: JPEG, PNG or WebP

The working rule: photographic artwork goes out as JPEG at quality 80 to 90 and needs no further thought. Flat graphics or crisp text keep their edges in PNG, but check the result against the placement cap — the 2 MB YouTube thumbnail limit and the 5 MB X in-stream limit are both easy to breach with a large PNG. WebP is the better compromise wherever the upload path accepts it.

Being under a cap is not a target to aim at. There is nothing to gain from shipping a 7.9 MB file to a placement that allows 8 MB when the platform re-encodes it to a fraction of that anyway. Optimise to the smallest size that still holds up at 100%, and leave the headroom unused.

Working one asset across several placements

Most teams cannot art-direct every placement separately. A workable compromise is three crops per campaign asset, which between them cover the bulk of day-to-day publishing.

What this does not cover is the extreme letterbox formats — the LinkedIn company cover at 5.9:1, the X header at 3:1 and the Facebook cover at 2.63:1. Those are profile furniture that changes rarely, so build them once, properly, with the avatar and UI overlays accounted for.

Before you publish

1. Run the final export through the checker and read the failures rather than the passes.
2. For any placement failing on ratio, re-crop from the master instead of stretching or padding.
3. Confirm the width clears the recommended figure, not merely the minimum, for anything appearing on a phone screen.
4. View the image at the size it will actually be seen — a tile in a grid, not a full-screen preview.
5. Check the file size against the cap of the tightest placement in the set.

Frequently asked questions