How to Resize an Image for Free Online

Uploading an image at the wrong dimensions causes two distinct problems: if it's too large, it slows down your page or gets compressed badly by the platform. If it's too small, it appears blurry when displayed at full size. Getting the dimensions right before uploading saves you from either problem — and it's straightforward once you know the target dimensions for the platform you're using.

Platform dimensions worth knowing

Every major social platform has its own recommended image dimensions. Using the right size means your image is displayed without cropping, stretching, or compression artefacts.

• Instagram square post: 1080 × 1080px
• Instagram portrait post: 1080 × 1350px
• Instagram Story / Reel: 1080 × 1920px
• Facebook post image: 1200 × 630px
• Twitter/X in-stream photo: 1600 × 900px
• LinkedIn shared image: 1200 × 628px
• Open Graph / blog OG image: 1200 × 630px
• YouTube thumbnail: 1280 × 720px (16:9)

These change occasionally as platforms update their specifications. When in doubt, check the platform's current media guidelines or upload a test image to see how it renders.

Understanding pixels vs file size

Image dimensions (pixels) and file size (KB/MB) are related but different. A 4000 × 3000px image at low quality might be smaller in file size than a 1200 × 800px image saved at maximum quality. When preparing images for the web, you generally want to control both: resize to the target dimensions, then compress to a reasonable file size (typically under 200KB for most uses).

Resizing and compressing are two different operations. An image resizer changes the pixel dimensions. An image compressor reduces the file size. For best results, resize first to the target dimensions, then compress.

Maintaining aspect ratio

The aspect ratio is the proportional relationship between width and height. A 1200 × 630px image has an aspect ratio of approximately 1.9:1. If you resize it to 1200px wide but change the height to 400px, the image becomes distorted — stretched horizontally.

Always resize with the "constrain proportions" or "lock aspect ratio" option enabled unless you specifically want a different aspect ratio. Our image resizer maintains proportions by default — enter either width or height and the other dimension adjusts automatically.

When you want to resize to exact dimensions

For platforms that require exact dimensions (like an Instagram square at exactly 1080 × 1080px), you'll need to both resize and crop. Resize to ensure the shortest dimension is at least 1080px, then crop to 1080 × 1080px, choosing which part of the image to keep. This workflow handles the majority of social media image preparation needs without Photoshop or any desktop software.