What this tool does
Automatically adjusts image quality to produce a file at or just under your target KB size. Uses iterative quality adjustment, not pixel resizing, to hit the target without changing image dimensions.
Image tool
Resize Image by KB Online
Resize any image to hit a specific file size target — useful for forms, job applications, or upload portals with strict KB limits. Set your target size in KB, upload your image, and download the result. Runs in your browser.
Complete guide
How to use Resize Image by KB Online
Image tools guide for resize image by kb online users.
Many websites and forms impose strict file size limits — a passport photo under 100 KB, a job application under 200 KB, a profile picture under 50 KB. Hitting an exact target is tricky with a quality slider because the relationship between quality and file size is non-linear and varies by image.
Resize by KB solves this automatically. The tool uses a binary search algorithm: it tries different quality levels, measures the output size, and iterates until the output is at or just under your target — typically within 1–5% of the target in 3–5 iterations.
All processing runs in your browser. No upload, no server. Works for JPG, PNG, and WEBP images.
How to use it
Upload your image, enter the target size in KB (e.g. 100), and click Convert. The tool iterates quality settings to produce a file at or under that size. Download the result.
Best practices
Enter a target slightly lower than the strict limit — e.g. 95 KB if the limit is 100 KB — to give a safety margin. Very small targets (under 20 KB) will result in visible quality reduction for most photos.
Quick checklist
- Confirm the input file, value, text, or measurement is correct before running the tool.
- Use the visible dropdowns and settings to choose the output format, unit, quality, size, or result style.
- Check the preview, result text, or downloaded file before using it for important work.
- For private or sensitive data, prefer browser-based tools and avoid uploading files unless the tool clearly needs server processing.
Answers
Resize Image by KB Online FAQs
Does reducing file size change the image dimensions?
No. This tool reduces file size by lowering quality (compression), not by shrinking the pixel dimensions. Your image stays the same width and height.
What if the target size is too small to achieve without extreme quality loss?
The tool will reach the minimum quality threshold and produce the smallest file it can. For very small targets, the result may show visible compression artefacts.
What formats are supported?
JPG, PNG, and WEBP. For PNG, quality reduction works by converting to a lower bit-depth or reducing the colour palette.
Is my image uploaded to a server?
No. This tool runs entirely in your browser. Your image never leaves your device.
Can I also change the image dimensions?
Not with this tool. Use Image Resize to change pixel dimensions, then use Resize by KB if you still need to hit a file size target.