Image Compressor
Compress images by adjusting JPEG quality. Runs entirely in your browser — nothing is uploaded.
Pure browser JavaScript (HTML canvas) — no upload.
How to use this tool
- Choose an image.
- Drag the quality slider to balance size vs. quality.
- Click Download compressed.
Compress images by adjusting JPEG quality. Runs entirely in your browser — nothing is uploaded.
How it works
The Image Compressor reduces the file size of JPEG images by adjusting the compression quality level. Drop or select an image file, move the quality slider to your desired setting (higher means better quality but larger file; lower means smaller file but more visible compression artifacts), and download the compressed result.
All processing happens in your browser using the HTML5 Canvas API. The image is decoded, re-encoded at the new quality level, and offered for download -- nothing is uploaded to any server.
This tool is useful for reducing image sizes before attaching them to emails, uploading them to web pages, or storing on devices with limited space. A quality setting of 70-80% typically gives a good balance between visual quality and file size reduction for photos.
Note that JPEG compression is lossy -- each re-save at a reduced quality permanently removes some image data. Start from the original file rather than a previously compressed version to avoid compounding quality loss.
Worked example
Compress a product photo for a website
- Select your original product JPEG (e.g., 4 MB from a camera).
- Set quality to 75%.
- Preview the output image to check that details are still clear.
- Note the new file size shown below the preview.
- Download the compressed image and use it on your website.
A compressed JPEG typically 60-80% smaller than the original, with no visible quality loss at 75%.
Common mistakes to avoid
- Compressing an already-compressed JPEG again instead of starting from the original, which doubles the quality loss and quickly degrades the image.
- Setting quality to an extremely low value (under 40%) for photos where fine detail matters, producing blocky or smeared results.
- Expecting lossless compression -- JPEG always discards some data; if you need lossless, use PNG format instead.
Key terms
- JPEG quality
- A scale from 1 to 100 controlling how much data is discarded during JPEG compression; higher values preserve more detail.
- Lossy compression
- A compression method that permanently removes some image data to achieve smaller file sizes, unlike lossless compression which can perfectly reconstruct the original.
- Compression artifact
- A visible distortion (blockiness, banding, ringing around edges) that appears in images compressed too aggressively.
Frequently asked questions
- Is my image uploaded?
- No — compression happens locally via the Canvas API.