Image Compressor & Converter
Compress and convert JPEG, PNG, WebP and AVIF images in batches, with before-and-after sizes for every file and an optional resize that usually saves more than the quality slider does. Images are decoded and re-encoded by your own browser, so there is no upload, no queue, no file-size cap and no privacy trade-off.
- Price:
- Free, no sign-up
- Data:
- Processed locally
- Reviewed:
Interactive image compressor
Settings
Parameters & SettingsChange anything and re-run — the originals stay on your device
Drop images here
JPEG, PNG, WebP, AVIF, GIF or SVG · batches welcome · nothing is uploaded
No images yet
Drop a batch above. Everything is decoded and re-encoded by your own browser.
How do I compress a PNG without losing quality?
PNG is lossless, so re-encoding it cannot make it meaningfully smaller. Convert it to WebP instead, which is typically 25 to 35% smaller at matching quality and supports transparency, or resize it — halving both dimensions quarters the pixel count and usually cuts file size by 70% or more with no visible change at display size.
How to use the image compressor
- Add images: Drop files onto the zone or pick them — batches are fine.
- Choose format and quality: Pick WebP, JPEG, PNG or AVIF and drag the quality slider.
- Optionally resize: Cap the longest edge to cut file size dramatically for web use.
- Download: Save images individually or get the whole batch as a zip.
How the image compressor works
What actually makes an image large
Dimensions dominate. A 4000×3000 photograph has 12 million pixels; displayed in a 800px-wide column it wastes roughly 96% of them. Resizing before compressing almost always beats tuning the quality slider — halving both dimensions quarters the pixel count and typically cuts file size by 70% or more with no visible change at display size.
Lossy and lossless
JPEG, WebP and AVIF are lossy: they transform the image into frequency components and discard those the eye is least sensitive to, especially in chroma. PNG is lossless — it compresses with a prediction filter plus DEFLATE, so it can only exploit genuine redundancy, which is abundant in flat graphics and scarce in photographs.
Why re-compressing degrades
Each lossy encode quantises what the previous one already quantised, and the errors accumulate — visible as blocking around edges and colour bleeding. Always re-encode from the highest-quality original you have rather than from an already-compressed copy, and avoid round-tripping the same file repeatedly.
Alpha channels
Converting a transparent PNG to JPEG discards the alpha channel; the tool composites onto a background colour you choose, rather than silently producing black fringes. If you need transparency and small files, WebP is the answer.
Image Compressor — frequently asked questions
No — and this is the main reason to use a client-side compressor. Files are decoded onto a canvas and re-encoded by your browser own image encoder. Nothing touches a network, so private photographs, screenshots containing credentials and unreleased artwork are all safe.
WebP for almost everything on the web: typically 25-35% smaller than JPEG at matching quality, with transparency support and universal browser support today. AVIF compresses harder still and encodes slowly. Keep PNG only for pixel art, screenshots of text, or images needing lossless transparency.
It sets the encoder quantisation level. Above about 0.85 you are mostly adding bytes for differences nobody can see; 0.75-0.82 is the sweet spot for photographs. Flat illustrations tolerate far lower settings than photographs with fine texture.
PNG is lossless, so re-encoding cannot discard detail and the quality slider does not apply. If a PNG grows, the original was already optimised — convert it to WebP instead, or resize it, which is where the real savings live for oversized images.
Official resources & government references
Verified references, primary standards specifications, and official publications governing the rules and calculations implemented in this tool:
W3C HTML5 Canvas 2D Context Specification
The international open standard governing pixel manipulation, image rendering, and canvas export formats.
WebP Image Compression Architecture & Format
Normative specification for lossy and lossless WebP image compression with alpha channel support.
Important Disclaimer
Images are compressed and converted in client-side memory using the HTML5 Canvas API without transmitting files to any server. Always keep master copies of original high-resolution photos before replacing assets.