Image Compressor
Slide the quality down and watch the file size fall.
What the quality slider actually does
JPEG compression works by throwing away detail your eye is least likely to notice — fine colour variation first, then fine texture. The quality number decides how aggressive that is.
Where to set it
- 90–100 — almost indistinguishable from the original, but the files stay large. Above about 95 you are mostly adding bytes for no visible gain.
- 75–85 — the useful range for the web. Most people cannot tell 80 from 100 on a photograph, and the file is often half the size.
- 50–70 — visible softening in flat areas like skies, but acceptable for thumbnails.
- Below 50 — blocky artefacts around edges, and obvious ringing around text.
Compression is one-way
The discarded detail is gone. Saving at 50 and then re-saving at 95 does not recover anything — it produces a larger file containing the same damaged image. Always compress from the original, not from a compressed copy.
This is also why repeatedly editing and re-saving a JPEG degrades it a little each time, the effect people call generation loss.
Resizing beats compressing
If an image is 4000 pixels wide and will be displayed at 800, no quality setting will help as much as resizing it will. Reduce the dimensions first, then compress. Doing both usually takes a 5 MB phone photo under 200 kB with no visible difference at the size it is shown.
Some images do not compress well
Screenshots, line drawings and anything with text or sharp edges come out badly as JPEG at any quality, because the format is built for gradual variation. Those belong as PNG, which is lossless and usually smaller for that kind of picture anyway.
Common uses
- Speeding up a website, where images are almost always the largest thing on the page.
- Getting under an upload limit.
- Email attachments and messaging apps.
- Saving storage on a large batch of photographs.
Questions people ask
What quality setting should I use?
75–85 for most web use. Most people cannot distinguish 80 from 100 on a photograph, and the file is often half the size.
Can I undo compression?
No. The discarded detail is gone. Re-saving at a higher quality makes a bigger file of the same damaged image.
Why did my screenshot look terrible?
JPEG is built for photographs, not sharp edges and text. Use PNG for screenshots.
Should I compress or resize?
Resize first if the image is larger than it needs to be. It saves far more than any quality setting.
Your image is not uploaded
This is the part worth being precise about, because almost every other site offering these tools works differently.
When you choose a file here, your browser reads it from your disk into memory and draws it onto a canvas. The work happens on your own machine. No copy is transmitted, because this site is a set of static files with no server behind it capable of receiving one.
The practical consequences: it works with no internet connection once the page has loaded, there is no file size limit beyond your own memory, there is no queue, nothing is retained on anyone's disk afterwards, and your photographs are not passing through a third party's infrastructure.
You do not have to take that on trust. The about page lists every network request this site makes, read live from your own browser.