How this image compressor handles each format
JPG and WebP are lossy formats. To reduce JPG size, lower the slider: it throws away fine texture you rarely notice. This photo compression happens in your browser. Photo details such as camera data and GPS location are not copied into the compressed file.
PNG is lossless, so a quality setting does not apply in the same way. FileKiwi sends PNG files to its server and reduces the number of colors: 256 at 85% or more, 192 from 60%, 128 below that. A screenshot of a settings page or a bar chart often shrinks a lot this way and still looks the same.
Other formats are turned into a common one by default. HEIC, AVIF and TIFF photos are saved as JPG. GIF and BMP files are saved as PNG. A GIF keeps only its first frame, so an animated GIF comes out as a still picture.
Three habits help:
- Crop first. Cutting away empty floor or sky saves bytes before compression even starts.
- Start from the original. Every new save of a JPG loses a little more, so compress the best copy you have.
- Match the format to the content. Photos belong in JPG or WebP. Logos, text and transparent backgrounds fit PNG.
Which format gives the smallest file?
The format often matters more than the slider.
| Format | Best for | Keep in mind |
|---|---|---|
| JPG | Photos for email, forms and social media | Opens everywhere, no transparency |
| WebP | Photos and graphics on websites | Usually smaller than JPG at similar quality, but some older apps cannot open it |
| PNG | Screenshots, logos, images with transparency | Heavy for photos, good for flat colors and text |
A camera photo saved as PNG is the most wasteful case. Switch the output to JPG and it usually drops to a fraction of its size. Note that JPG has no transparency, so see through areas turn white. If you need an image optimizer for a website, choose WebP: it is usually smaller than JPG at a similar look, so pages load faster.
Reduce image file size to a limit in KB or MB
Upload forms often name a limit such as 50 KB, 100 KB or 1 MB. The slider on this page does not aim for a number, but the size pages do, and they work as a KB or MB reducer. They search for the highest quality that fits and lower the pixel dimensions only when needed: compress image to 20 KB, to 50 KB or to 100 KB.
For a limit in MB, open any of those pages and type your own target in the Target size box, which takes 5 to 20000 KB. Type 950 to compress an image to a little under 1 MB, or 1900 for 2 MB. Those numbers stay under the limit both when a form counts 1 MB as 1,000,000 bytes and when it counts 1,048,576.
A 4000 pixel wide photo is also far bigger than any blog column or chat window. Lowering its width with Resize Image before you compress gives the biggest drop. For photos only in JPG, Compress JPG keeps everything in that format, and Compress PNG does the same for PNG.
Reduce image quality on purpose
Sometimes you want the opposite of a sharp picture: a low quality image for a meme, a draft preview or a test. This page works as an image quality reducer too, so you can make an image low quality on purpose. Drag the slider down to 30% and save as JPG or WebP, and the result shows blocky edges and smeared detail. To make an image look even rougher, compress the result a second time, or shrink it with Resize Image before you compress it.