Image Compare Slider
Technical details
How the Image Compare Slider Works
What the Tool Does
The Image Compare Slider overlays two images and exposes only the part you want to see by dragging a vertical handle. As you slide left and right, more of the 'before' or 'after' image is revealed, making side-by-side visual differences immediately obvious. File sizes and percent-change are displayed so you can see the byte-level impact too.
Common Developer Use Cases
Engineers verifying lossy image compression compare a JPEG vs. WebP version of the same source. Designers review tone-mapping, retouching, or color-correction changes between a draft and final version. ML/AI engineers visualize super-resolution, denoise, or style-transfer results against their inputs. Marketing teams produce dramatic before/after demos for landing pages.
Data Formats, Types, or Variants
Accepts any image format the browser can render — PNG, JPEG, WebP, AVIF, GIF, SVG. Images stay in your browser via object URLs (URL.createObjectURL), so nothing is uploaded. For the most useful comparison the two images should have matching dimensions and aspect ratio; if they differ, both render with object-fit: contain so neither is cropped.
Common Pitfalls and Edge Cases
Comparing images of different aspect ratios produces letterbox bars on one side. Very large images (>50 MB) may slow down the drag interaction in older browsers. The slider exposes the entire 'after' image — if both files have transparency, position the slider over an opaque area or you'll see the page background bleeding through both panes.
When to Use This Tool vs Code
Use the browser tool for ad-hoc comparison during development or for quick stakeholder demos. In production websites, integrate dedicated libraries like react-compare-slider or img-comparison-slider for accessibility, lazy loading, and SSR support; for batch automated quality checks across hundreds of images, use SSIM/PSNR-based tools like ImageMagick `compare` or pixelmatch.