Why Platforms Recompress Your Images
When you upload an image to Instagram, LinkedIn, or Twitter/X, the platform doesn't store your original file. It processes the image through its own compression pipeline, generating multiple variants at different resolutions for different device types and network speeds — thumbnail, medium, full-size mobile, desktop, and so on.
This pipeline is optimized for the platform's storage costs and delivery performance, not for your image quality. If your original file is large and uncompressed, the platform has more data to work with and typically produces better-looking output. If your original was already heavily compressed — say, a JPEG saved at 60% quality — the platform's compression stacks on top of the existing compression artifacts and visibly degrades the result. You'll see banding in gradients, blockiness around text, and loss of detail in faces and fine textures.
The practical implication: submit images as close to the platform's native resolution as possible, at a relatively high quality level (85%+ for JPEG, or PNG for graphics). Don't pre-compress to save upload time — the platform will compress anyway, and giving it a high-quality source produces better results.
Recommended Dimensions by Platform
Getting dimensions right means the platform doesn't need to scale your image before applying its own compression. Scaling adds another quality loss step.
For Instagram, a square post should be 1080×1080 px. Portrait posts (the most common format for single-image posts, since they take up more screen real estate in the feed) should be 1080×1350 px — the maximum allowed aspect ratio before Instagram crops. Stories and Reels use the full vertical format at 1080×1920 px.
LinkedIn article thumbnails and link previews display at 1200×627 px. Profile banner images are 1584×396 px. For regular post images, 1200×628 px is a safe target that displays well across both desktop and mobile feeds.
Twitter/X displays images at 1200×675 px for standard landscape posts (the 16:9 format). A single vertical image should be 1200×1350 px to fill more screen space in the timeline.
TikTok thumbnails and vertical video exports are 1080×1920 px (9:16). For cover images, keep important content centered — the top and bottom 14% may be cropped depending on the display context.
Format to Use Before Uploading
For photographs and images with gradients — portraits, landscapes, product photos — use JPEG at 85% quality. WebP is technically superior at equal quality, but not all platforms handle WebP uploads consistently. Instagram in particular converts WebP in ways that can produce unexpected color shifts. JPEG remains the safest cross-platform choice for photographic content.
For graphics with sharp edges, text, logos, and flat color areas, use PNG. JPEG compression creates "ringing" artifacts — halos of discoloration — around sharp color transitions. The blockiness is especially visible around letters. A PNG uploaded with crisp text will remain crisp after the platform's compression because the source has no pre-existing artifacts for the compression to amplify.
Always work at the exact recommended dimensions. A 4000×4000 pixel image uploaded to Instagram will be scaled down to 1080×1080 px during processing — you've added upload time without any quality benefit. Resize to the target dimensions before uploading.
Test Before Publishing
The quality after platform recompression varies more than most people expect, and it varies based on content. A portrait with smooth skin tones may look perfectly fine after compression, while a similar image with a bold text overlay may show visible blockiness around the letterforms.
The reliable way to know how your specific image will look is to test it. Upload a version to a private or archived post, then view it at full size on both mobile and desktop. Zoom into text elements and face regions — these are the areas that suffer most from aggressive JPEG compression.
If the result is unsatisfactory, try uploading a PNG version instead. PNG files are larger and take longer to upload, but they give the platform's compression a loss-free source, which often produces cleaner output. For images that will be pinned, featured, or used in advertising campaigns, this extra step is worth the effort.