Short, direct answers to the questions people ask most about compressing images. For the full walkthrough, see the complete Image Compressor guide.
The basics
What is image compression? It reduces an image's file size by re-encoding it more efficiently and, for lossy formats, discarding data the eye cannot detect. The image looks the same but is far smaller.
What is the difference between lossy and lossless? Lossy (JPEG, WebP) permanently removes some data for much smaller files. Lossless (PNG, lossless WebP) keeps every pixel, so there is no quality loss but files are larger.
Does compressing reduce quality? At 75–85% quality the loss is invisible while the file drops 60–90%. Lossless compression changes size with no quality loss.
Settings and formats
What quality setting should I use? About 80% for photos; 90%+ for images with text or sharp edges.
Which format is smallest? WebP — typically 25–35% smaller than an equal-quality JPEG.
When should I use PNG instead of JPEG? For logos, icons, screenshots, line art and transparency. Use JPEG or WebP for photos.
Can I compress a PNG without losing transparency? Yes — output PNG or WebP. JPEG removes transparency.
Size and dimensions
How much smaller can I make a photo? A 4–6 MB smartphone photo usually drops to 300–800 KB — around 85–90% smaller.
Does resizing reduce file size? Yes, often more than compression. Halving width and height cuts pixels by 75%.
What is the best image size for a website? Hero images under ~200 KB, content images under 100 KB, served at no more than 2× their displayed size.
Why is my PNG so large? PNG is lossless and stores every pixel, so photos become huge. Use JPEG or WebP.
What is the difference between compressing and resizing? Compressing keeps dimensions and shrinks the file; resizing reduces the dimensions. Do both for the best result.
Quality, privacy and metadata
What DPI should images be? For screens, DPI does nothing — only pixel dimensions matter. DPI affects print only.
Is it safe to compress images online? Only if the tool does not upload your files. The Aizen Image Compressor runs in your browser, so images stay on your device.
Will compression remove EXIF metadata? Re-encoding usually drops EXIF, which shrinks the file and removes GPS data.
Does compressing multiple times degrade the image? With lossy formats, yes — artifacts accumulate. Compress once from the original.
Do I need to install software? No — it works in any modern browser, no sign-up or watermark.
Is there a file-size limit? No server cap; the practical limit is your device's memory.
Ready to compress? Open the Image Compressor, or read the step-by-step guide to compressing without losing quality.