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Social media image resizer

Pick a network and where the image goes, drop it in, and download one that fits: the right shape, the right size and under the file cap, for Threads, X, Bluesky, Mastodon, LinkedIn, Instagram, Facebook and TikTok.

Runs in your browser. Your text and images never leave it.

Updated

Network

Where it goes

  • Up to 8 MB
  • JPEG, PNG
  • We make 1,440 px wide at most

Drop an image here

or

JPEG, PNG, WebP or GIF. It stays on your device. Nothing's uploaded.

Your image

Your resized image shows up here.

Shape

Save as

0 / 1,000

Describe the image for people who can't see it. Copy it into the post with the image. Threads doesn't say how it counts, so we count the strictest way.

How it works

  • Pick the network and where the image goes: a post, several images, a profile photo, a header or a link card.
  • Drop in a JPEG, PNG, WebP or GIF. It's read and drawn in your browser, and nothing's uploaded.
  • Pick a shape. Drag on the image, or use the arrow keys, to choose what stays in the crop. Or fit the whole image inside and fill the edges with a blurred copy or a colour.
  • Download it. The file's named for where it goes, like beach-bluesky-post-2666x4000.jpg. The alt text box counts the way that network does, so you can write the description while you're there.

How it gets under the cap

If the file is over the network's cap, the resizer saves it again at lower quality: 85, then 80 down to 25. If that's still too big, it scales the image down in steps to half its size, lowering the quality as it goes, and keeps the first try that fits. It aims 5% under the cap, because a network may count a file's size a little differently from your browser.

Most networks write their caps in MB. We read them as decimal, so 5 MB is 5,000,000 bytes, unless the network's own code says otherwise. Mastodon's does: its 16 MB is 16,777,216 bytes.

It never enlarges an image: a small one stays small, and it tells you if that's under the network's minimum. Very large photos, over about 16.8 megapixels, are read at that size so a phone doesn't run out of memory.

Formats, HEIC and GIFs

It saves JPEG, PNG and, where your browser can write it, WebP, and only the formats the placement takes. An image with transparency starts as a PNG; a JPEG fills clear areas with white.

HEIC photos from an iPhone open where the browser can read them, and Safari can. Elsewhere, the resizer tells you how to get a JPEG instead.

Resizing an animated GIF, PNG or WebP keeps only its first frame. So for a moving image, you can keep the original file as it is, and the resizer checks it against the network's limits for animated images.

A post image on each network

Post image sizes on each network
NetworkFile sizeWe makeOne image's shape
Threads8 MB1,440 px wide at mostNot documented
X5 MB4,096 px on the long edge3:4 to 2:1 shown whole
Bluesky2 MB4,000 px on the long edgeTaller than 1:2 is cropped
Mastodon16 MBup to 8.3 megapixelsIts own shape
LinkedInNot published4,096 px on the long edgeNot documented
Instagram8 MB1,080 px wide at most3:4 to 1.91:1 shown whole
Facebook10 MB2,048 px on the long edgeNot documented
TikTok20 MB1080 × 19209:16

Where a network gives a size, we make that size. Where it only gives a limit, like Threads' 1,440 px, Bluesky's 4,000 px or Mastodon's 8.3 megapixels, we make the largest it keeps. Where it gives neither, we pick one and say so: X and LinkedIn post photos at 4,096 px, X's link card at 1200 × 600, Bluesky's avatar at 1,000 px and LinkedIn's profile photo at 800 px.

Does Shaflex check my images for each network?

Yes. Shaflex checks every image you attach against the media rules of each network you post to, across Threads, X, Bluesky, Mastodon and LinkedIn. If a network can't take an image, the post still goes to the networks that can, with a note saying why. The image editor works inside your draft: crop to a network's size, put a screenshot in a device or on a backdrop, and blur what's private.

See how Shaflex schedules for Threads, X, Bluesky, Mastodon and LinkedIn, how one draft goes to every network, and what the free plan includes.

Where these rules come from

Each one is from the network's own documentation, help pages or source code. We last checked them on .

More free tools

Each one runs in your browser too.

Questions

Is my image uploaded anywhere?

No. It's read, cropped, drawn and saved in your browser. Nothing leaves your device, and there's nothing to sign up for.

Why is my image smaller than the size you list?

The resizer never enlarges an image, because that only blurs it. If your crop is smaller than the placement's size, it keeps your size and tells you so.

Can it open HEIC photos from an iPhone?

Where the browser can read them, yes, and Safari can. Elsewhere, open the photo in Photos and share it as a JPEG, or set your iPhone's camera format to Most Compatible.

Does it keep GIFs animated?

Resizing keeps only the first frame. For an animated image you can keep the original file instead, and the resizer tells you if it breaks the network's limits for animated images.

Which networks and placements does it cover?

Threads, X, Bluesky, Mastodon, LinkedIn, Instagram, Facebook and TikTok: post images, several images, profile photos, headers, link cards and stories, wherever the network documents them. Where it doesn't, the guide says so and the size is our pick.

Write the next post once.

Shaflex fits it to Threads, X, Bluesky, Mastodon and LinkedIn, schedules it on your rhythm and brings the replies back to you.

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Free plan, no card needed.