About this tool
The Image KB Reducer is the general-purpose version of our KB compression tools, built for anyone who needs an image under a specific file size that isn't covered by a fixed preset — whether that's optimizing a photo for faster website loading, meeting an unusual upload limit, or shrinking a large camera photo before emailing it. Enter any target size in KB (or pick a quick preset like 10KB, 20KB, 50KB, 100KB, or 200KB) and the tool uses a binary-search algorithm to find the highest JPEG quality that still fits under your limit, falling back to proportional dimension scaling if quality adjustments alone aren't enough. A before-and-after preview shows the resulting file size and dimensions so you can confirm it meets your needs before downloading. All processing happens locally in your browser using the HTML5 Canvas API — your image is never uploaded to a server.
How to use
- 1
Set a Target KB
Type your desired file size in KB or choose one of the quick presets.
- 2
Upload Your Image
Drag and drop or select a JPG, PNG, or WEBP file.
- 3
Download the Result
Check the before/after comparison and click Download to save the compressed file.
Features
- Compress to any custom target size in KB, or use quick presets (10, 20, 50, 100, 200, 500 KB)
- Binary-search algorithm finds the highest quality that fits your target
- Automatic proportional downscaling for very small size targets
- Side-by-side before/after preview with file size and dimensions
- Supports JPG, PNG, WEBP, and BMP input files
- Processed entirely in your browser — never uploaded to a server
Tips & common mistakes
- •For very low KB targets on high-resolution photos, expect some visible downscaling — the tool prioritizes fitting your size limit over keeping original dimensions.
- •If the output still looks larger than expected, check that your browser hasn't cached an older version of the file under the same name when downloading repeatedly.
- •PNG images with transparency are converted to JPEG with a white background fill, since JPEG doesn't support transparent pixels.
- •If you regularly need the same KB target (e.g., always 50KB), bookmark the dedicated 50KB tool instead of re-typing the number here each time.
Binary Search & Progressive Downscaling Algorithm
Balances quality and pixel dimensions to land as close as possible to your target size without exceeding it.
TargetBytes = TargetKB × 1024 | BinarySearch(Quality: 0.05–0.98) & AdaptiveScale(Width, Height)- •Initial check: measures file size at minimum quality to see if the target is reachable at full dimensions
- •Dimensional scaling: if even minimum quality exceeds the target, dimensions are scaled down proportionally
- •Binary search: tests quality midpoints across several iterations to find the highest quality where size stays at or under the target