A free, open-source image compressor that runs entirely in your browser. Your photos are never uploaded: compression happens on your own device. Output keeps the same resolution with near-identical quality, and JPEG photos keep their date taken, camera and location details.
You can compress many images at once and download them as a ZIP. If compression would not make a file smaller, you get the original back.
You need to enable JavaScript to use the app.
Source code on GitHub (MIT license)