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Convert a PDF Tools
Free · No sign-up · Runs in your browser

Compress an image.

This free compress image tool shrinks JPG and PNG file sizes for faster uploads and smaller attachments — batch process as many as you like, without a single file leaving your device.

Not uploaded — nobody sees it 3 compression levels No watermark, ever No subscription or account
Your files are never uploaded — they’re processed right here in this browser tab, on your device. There’s no server involved, so we never see them, copy them or keep them.
How it works

Three steps, no waiting on a server

Altto's compress tool works right in your browser tab using the canvas built into every modern browser, so there's no upload queue and no “processing your file” spinner tied to someone else's servers.

01

Add your images

Drop in one or more JPG or PNG files.

02

Pick a strength

Light, Medium or Strong — trade file size against quality.

03

Save your images

One downloads directly; several come back as a .zip.

Why this runs in your browser, not on a server

Photos often contain things you’d rather not hand to a stranger’s server just to shrink a file size. Altto skips that step completely — there’s no server for it to go to.

  • Nothing is uploaded, everEvery image is decoded and re-encoded using your browser’s own canvas, because there’s no server on the other end. That also means we can’t see it, copy it or keep it.
  • No account, no email wallCompress as many images as you like without signing up or handing over an email address.
  • Batch conversion built inAdd a whole folder of images at once and get them all back together.
0

images stored on our servers. There’s no server involved at all — each compressed image is built once, then everything happens locally.

FAQ

Frequently asked questions

The practical details on what this tool can and can’t do. Need to change format instead of size? See our other tools.

Why does the compressed file come back as JPG?
JPG’s quality setting is what actually shrinks a photo’s file size. If you upload a PNG, it’s re-encoded as a high-quality JPG so the size reduction is real — note this does flatten any transparency to white.
How much smaller will my image get?
It depends on the image, but Medium typically cuts photo file sizes by 60-80%. Try Strong if you need the smallest possible file and don’t mind a bit more softness.
Is my image uploaded anywhere?
No — nothing is ever uploaded. Every image is decoded and re-encoded entirely inside this browser tab using the canvas built into your browser. There's no server involved at all, so there's nothing for Altto to see, copy or keep.
Will I notice the quality loss?
At Light or Medium, most people can’t tell the difference at normal viewing sizes. Strong trades more visible quality for a smaller file.
Can I compress several images at once?
Yes — add as many images as you like. One downloads directly; more than one comes back as a .zip.
Do you keep a copy of my images?
No. There's no upload, so there's nothing on our side to keep. See the Privacy Policy for details.
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