TinyPNG
tinypng.com
Shrinks PNG and JPEG files by half with no visible difference
No sign-upClassic
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squoosh.app
Compare image compression settings side by side before you export.
A split-screen image compressor from the Chrome team: original on the left, your chosen codec and quality on the right, with the file size updating as you drag. It handles MozJPEG, WebP and AVIF, and the whole thing runs in the page, so images are never uploaded. The interface assumes you know roughly what a codec is, which makes it excellent for one careful export and slow for a folder of two hundred.
AltFTool does this too
If you would rather not leave the site, Image Compressor covers the same job here — free, no account, and it runs in your browser.
Open Image CompressorQuestions
Works the moment the page loads. No account, no email, no trial. One image at a time — there is no batch mode.
No. Squoosh does the work inside your browser, so the file never leaves your device — you can load the page, disconnect from the network, and it still works. That makes it a reasonable choice for material containing personal data.
One image at a time — there is no batch mode.
Alternatives
Same category or same task, ordered by how closely they overlap.
tinypng.com
Shrinks PNG and JPEG files by half with no visible difference
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iloveimg.com
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photopea.com
Opens a PSD, keeps the layers, and runs entirely in a browser tab
screely.app
Wraps a raw screenshot in a browser frame and a decent background