Free tool · No signup · Runs in your browser
Social media image size checker
Choose an image and see immediately which networks will accept it: format, file size, aspect ratio and pixel limits, checked against the same rules SimplePost uses before publishing. The file stays on your device.
The file is read in your browser and never uploaded.
Results by network
Choose a file to compare it with each network's rules.
How to use it
How to use the image size checker
Choose the image
Use the exact file you plan to post; exports can change the format and size.Read the results
Each network shows OK, Check or Fix with the reason.Export again if needed
Common fixes: save as JPEG for Instagram, crop to 4:5, compress under 2 MB for Bluesky or 4 MB for Facebook.Upload in SimplePost
Attach the image in the composer or give your assistant a public URL.
What it checks
Image rules by network
Instagram accepts only JPEG images between 4:5 portrait and 1.91:1 landscape. Bluesky limits images to 2 MB and Facebook to 4 MB. TikTok photo posts accept JPEG or WebP up to 1080 × 1920. Pinterest prefers 2:3. YouTube posts take a video, not an image. Hosted SimplePost also caps uploads at 50 MB per file in the web app and 500 MB through MCP, the API and the CLI.
| Network | Formats | Max size | Per post | Shape |
|---|---|---|---|---|
| X | Any accepted type | 5 MB | Up to 4 | – |
| Any accepted type | no limit | Up to 9 | Up to ~36 MP | |
| JPEG | 8 MB | Up to 10 | 4:5 to 1.91:1 | |
| Any accepted type | 4 MB | Up to 10 | – | |
| Threads | JPEG, PNG | 8 MB | Up to 20 | – |
| Bluesky | JPEG, PNG, WEBP | 1.9 MB | Up to 4 | – |
| TikTok | JPEG, WEBP | 20 MB | Up to 35 | Up to 1080 × 1920 |
| YouTube | Video only | |||
| JPEG, PNG | 20 MB | Up to 1 | 2:3 recommended | |
| Telegram | Any accepted type | 10 MB | Up to 10 | Up to 20:1; w+h ≤ 10,000 px |
FAQ
Image size checker questions
What image size is best for Instagram?
A JPEG at 4:5 portrait (for example 1080 × 1350) or 1:1. Instagram rejects images narrower than 4:5 or wider than 1.91:1 and files over 8 MB.
Why does Bluesky reject my photo?
Bluesky limits each image to 2,000,000 bytes. Compress the image or export it at a smaller size.
Is my image uploaded?
No. The browser reads the file's type, size and dimensions locally. Nothing is sent to SimplePost.
Does SimplePost resize images automatically?
Not by default. SimplePost validates the image and tells you what to change, so the published image is exactly the one you chose.
Next steps
From checked draft to scheduled post
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