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There are tons of websites that will let you quickly upload and resize any image file, including JPEG files. Some of them allow you to resize multiple images at once. Search "resize jpeg" to find a bunch of different options. Resizing using a website is most effective while using a computer, not a mobile device. Some of the more popular sites include:  picresize.com resizeyourimage.com resizeimage.net Most resizing sites allow you to upload virtually any type of image file. Click the "Choose file," "Upload image," or "Browse" button to find the image file on your computer that you want to resize. If the image you want to resize is on another website, you'll need to download it to your computer first before uploading it to the resizing website. Each website has a different set of controls to adjust the image size. You may be able to click and drag a box, or use sliders to adjust the final size. You may also be able to enter the exact dimensions you want the resized image to be. Making an image larger than the original will result in a noticeably lower-quality picture. Some resizing websites allow you to set a compression level. Higher compression will result in a smaller file size, but will also lead to a decrease in image quality. Look for a quality slider or drop-down menu to change the final quality. Not all resizing websites have quality options. Once you've set your size and quality settings, you can resize and download the image. Click the "Resize" button to load the new image. You'll likely be shown a preview of the changes before the image file is downloaded to your computer. When downloading a resized image, make sure you don't overwrite the original. This will allow you to go back and make changes if you aren't happy with the outcome.
Visit an image resizing website. Upload the JPG file you want to resize. Use the resizing controls to change the size of the image. Select your compression (if available). Download the resized image.