Image Compressor
Compress many photos at once by quality or to a target size in KB
How to Use
- Drop one or more photos on the box, or tap it to choose them. You can keep adding files.
- Choose Quality and set the slider, or choose Target size (KB) and enter the largest size each file may be.
- Pick JPG (accepted everywhere) or WebP (smaller, keeps transparency).
- Tap Compress. Each file shows its size before and after and the percentage saved.
- Download files one by one with the download button, or tap Download all as ZIP.
How image compression works
JPG and WebP are lossy formats: when they save a picture, they throw away fine detail the eye is unlikely to notice. The quality setting (0–100%) controls how much is thrown away. A lower quality means a smaller file, but go too low and you will see blur, colour banding and blocky "artefacts" around edges and text.
This compressor redraws each photo on a browser <canvas> and saves it again as JPG or WebP. Everything happens on your phone or computer; the photos are never uploaded. You can compress many photos in one go and download them together as a ZIP.
Two ways to compress
Quality mode saves every photo at the quality you choose. It is quick and predictable: 70% is a good starting point for photos you will share or view on a phone.
Target size mode is for forms and portals that say "maximum 100 KB" or "under 200 KB". You type the limit and the tool searches for the best result under it:
2. Try quality 40%. If that fits, binary-search between 40% and 92%
(about 7 tries) for the highest quality that still fits.
3. If even 40% is too big, shrink the width and height.
New scale ≈ current scale × √(target ÷ size at 40%) × 0.95
(between 50% and 90% of the current size), then repeat from step 1.
File size grows roughly with the number of pixels, and the pixel count goes with the square of the scale. That is why the square root appears: to roughly halve the file you shrink each side to about 71%, not 50%. Quality is never pushed below 40% before the dimensions are reduced, because very low quality looks worse than a slightly smaller picture.
Worked example
A form asks for a photo under 100 KB and your phone photo is 3.2 MB at 4000 × 3000. At 40% quality the full-size file might still be around 600 KB. The tool estimates a new scale of √(100 ÷ 600) × 0.95 ≈ 0.39 but limits each step to 50%, so it tries 2000 × 1500. If that is now, say, 150 KB at 40%, the next step is √(100 ÷ 150) × 0.95 ≈ 0.78, giving about 1550 × 1163, and so on until a quality search succeeds under 100 KB. The real numbers depend on your photo; the list shows the final dimensions and quality used for every file.
What saving to expect
| Original | Typical result | Why |
|---|---|---|
| Phone camera JPG (several MB) | Large saving | Cameras save at very high quality |
| PNG photo or screenshot | Large saving as JPG/WebP | PNG is lossless, so photos in PNG are big |
| WhatsApp-forwarded image | Little or none | Already compressed once |
| Image already under 100 KB | May get bigger | Re-saving can't beat a well-compressed file |
If a file comes out bigger than the original, the list says so. In that case simply keep your original.
KB and MB
This tool counts 1 KB as 1024 bytes and 1 MB as 1024 KB, as Windows does. Some websites count 1 KB as 1000 bytes. If a portal's limit is strict, aim a few KB below it, or use the Exam Photo & Signature Resizer, which keeps the file inside the range under both definitions.
Tips
- Choose JPG for anything you will upload to a government or bank site; many accept only JPG/JPEG.
- Choose WebP for websites and to keep transparent backgrounds. A few older apps cannot open WebP files.
- Compression removes EXIF data such as GPS location, which is good for privacy when sharing.
- Don't compress the same photo again and again; each save loses a little more detail. Start from the original.