Free Online Image Compressor — No Upload
Your photo is decoded and edited in this tab. It stays local, including whatever its metadata says about where it was taken.
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How it works
What the quality slider actually changes
JPEG quality is not a percentage of anything. The number picks a scaling factor for the quantisation tables that decide how aggressively each 8×8 DCT block throws away high-frequency detail, which is why the file size curve is steep at the top and flat in the middle. Between 75 and 85 most photographs are indistinguishable from the original at normal viewing size; above 90 the file grows quickly for detail nobody sees. PNG has no such dial — it is lossless, so compressing it means better filtering and a smaller palette, not fewer pixels.
- JPEG quality
- A quantisation table selector, not a percentage. 75–85 is the usual knee; below 60 you start seeing blocking around edges.
- Chroma subsampling
- 4:2:0 stores colour at half resolution and is invisible on photographs. It smears saturated red-on-black edges, so screenshots and logos want 4:4:4.
- PNG re-encode
- Lossless. The same pixels come out smaller through better filtering and deflate. A photograph saved as PNG stays large — convert it instead.
- WebP quality
- Lossy WebP is typically 25–35% smaller than JPEG at matched quality. Encoded by a WASM codec so it works in Safari as well.
- Metadata
- Re-encoding drops EXIF, the embedded thumbnail and the ICC profile. On a phone photo that is often tens of kilobytes on its own.
How to use it
How to compress an image online
- 01
Drop the image in
JPG, PNG or WebP, read from disk with the File API rather than uploaded.
- 02
Move the quality slider
The before and after sizes update as you go, so you can stop at the point where the saving stops being worth it.
- 03
Download the result
The original file on your disk is never modified or replaced.
Where it earns its keep
Where image compression is the whole job
- Getting a 6 MB phone photo under an email or upload form's size limit.
- Cutting page weight before a hero image ships to production.
- Preparing photographs for a listing site that rejects anything over a few megabytes.
- Making a screenshot small enough to paste into a ticket without waiting on it.
Questions
Image Compressor, answered
Can it make a JPEG smaller without losing any quality?
No. JPEG is lossy, so a smaller file is always a file with less detail in it — the honest goal is a loss you cannot see, not no loss at all. If you need genuinely lossless compression, use PNG or lossless WebP and accept a much larger file.
Are my images uploaded to be compressed?
No. The file is read from disk, decoded and re-encoded inside this browser tab. Open your network inspector while you compress — no request carries the image, which is also why it keeps working offline.
Does compressing an already-compressed JPEG help?
Rarely, and it costs you. Each pass re-quantises pixels that were already quantised, so artefacts accumulate generation after generation. Go back to the original file and compress once rather than compressing an export of an export.
Why did my PNG barely get smaller?
Because it was probably already optimised, or it is a photograph. PNG compression is lossless and works on runs of similar pixels, which photographs do not have. Converting that PNG to JPEG or WebP is the change that moves the number.