Reduce JPEG file size by compressing the image quality or dimensions

A JPEG file gets smaller when you lower its quality setting or shrink its width and height in pixels. Most JPEG files are already compressed, so you cannot squeeze them much further without changing what the image actually looks like. The trade-off is straightforward: lower quality means smaller file, but blurrier or grainier results. For photos you are posting online or emailing, a quality setting between 70 and 85 percent usually looks fine while cutting file size in half.

You do not need special software to do this. Windows comes with Paint, macOS comes with Preview, and both can re-save a JPEG at a lower quality. Online tools like TinyJPG or Squoosh work in your web browser and let you see the before-and-after side by side. If you have dozens of photos, a batch tool like ImageMagick (command line, free) or Adobe Lightroom (paid subscription) can shrink them all at once.

Key Takeaways

  • JPEG files shrink when you lower the quality percentage or reduce the pixel dimensions — quality loss is the trade-off for smaller size.
  • Windows Paint and macOS Preview can re-save JPEGs at lower quality without buying anything.
  • Online tools like Squoosh or TinyJPG show you the quality loss before you save, so you can find the right balance.
  • If you need to shrink many photos at once, batch tools like ImageMagick or Lightroom process them all in one step.
  • Metadata (camera settings, location, date) adds a small amount of file size and can be stripped out separately if needed.

Using Windows Paint to lower JPEG quality

Open the JPEG in Paint (right-click the file, select "Open with", choose Paint). Go to File > Export As. In the dialog, select JPEG from the file type dropdown. Click the Options button that appears. A window opens with a Quality slider — move it left to reduce quality and file size. The default is usually around 95 percent; try 75 or 80 for a noticeable size reduction with acceptable image quality. Click Save.

Paint does not show you a preview of the quality loss before you save, so you may need to try a few times to find the right setting. If the result looks too blurry or grainy, open the original again and try a higher quality number. Keep the original file and save the compressed version with a different name so you do not overwrite it by accident.

Using macOS Preview to compress and resize

Open the JPEG in Preview (double-click it, or right-click and select Open With > Preview). Go to Tools > Adjust Size to change the pixel dimensions. Reducing width and height by 20 or 30 percent cuts file size noticeably without obvious quality loss in most photos. Click OK when done.

To lower quality, go to File > Export. In the dialog, make sure JPEG is selected as the file format. A Quality slider appears below — drag it left to reduce quality. Try 75 or 80 as a starting point. Give the file a new name and click Save. Like Paint, Preview does not show a live preview, so test a few settings on a copy of the original.

Online tools that show quality loss before you save

Squoosh (squoosh.app) and TinyJPG (tinyjpg.com) both let you upload a JPEG and see the compressed version side by side before you read it. Drag a quality slider or compression level and watch the file size number change in real time. This is faster than the back-and-forth of trying different settings in Paint or Preview.

Squoosh runs entirely in your browser, so the image never leaves your computer. TinyJPG uploads the file to their server, compresses it, and lets you read the result — they delete it after an hour. Both are free for a handful of images per month. For occasional use, either one is simpler than learning Paint or Preview.

Reducing pixel dimensions to shrink file size

A photo that is 4000 pixels wide takes up more space than the same photo at 2000 pixels wide, even at the same quality setting. If you are posting to social media or email, you rarely need the original full size. Most phones and cameras create images much larger than what a screen can display.

In Paint, go to Image > Resize. Change the width or height to a smaller number — the other dimension shrinks automatically if you have the chain link icon locked. Try reducing to 50 or 60 percent of the original size. In Preview, use Tools > Adjust Size and enter a new width. Reducing dimensions by 30 to 40 percent usually saves more space than lowering quality alone, and the image still looks sharp on a screen.

Removing metadata to save a small amount of space

JPEG files often contain hidden data called metadata — the camera model, date taken, GPS location, and other settings. This adds only a few kilobytes to most files, but if you are concerned about privacy or want to squeeze out every byte, you can strip it out. Online tools like Verexif (verexif.com) or Exif Purge let you upload a JPEG and read a version with metadata removed.

In most cases, removing metadata saves less than 5 percent of file size, so it is not worth the extra step unless you have a specific reason. If you are uploading photos to a website and do not want to share location data, it is worth doing. For email or social media, the size savings are too small to matter.

Batch processing many photos at once

If you have 50 or 100 photos to shrink, doing them one at a time in Paint or Preview takes hours. ImageMagick is a free command-line tool that can process all of them in seconds. read it from imagemagick.org, install it, then open a terminal or command prompt in the folder where your photos are. Type a command like: magick mogrify -quality 75 -resize 75% *.jpg. This reduces quality to 75 percent and shrinks dimensions to 75 percent of the original for every JPG file in that folder.

If command line feels unfamiliar, Adobe Lightroom has a batch export feature with a quality slider and dimension controls. It costs money, but the interface is visual and does not require typing commands. For most people, doing a few photos at a time in Squoosh or Preview is simpler than learning ImageMagick, but if you regularly work with large photo libraries, the command-line approach saves time.

Frequently Asked Questions

How much smaller can I make a JPEG without it looking bad?

Most photos look acceptable at quality 70 to 80 percent, which typically cuts file size in half. Below 60 percent, you start to see visible graininess or blurriness. The answer depends on the original image and what you are using it for — a photo for a website can go lower than one you are printing.

Should I reduce quality or dimensions to make a JPEG smaller?

Reducing dimensions (width and height) usually saves more space and keeps the image sharper. If your photo is 4000 pixels wide but you only need it for email or social media, shrinking to 2000 pixels saves significant space. Lowering quality works too, but dimension reduction is often the better choice.

Can I make a JPEG smaller without any quality loss at all?

No. JPEG is already a compressed format, so re-saving it always causes some loss. If you need lossless compression, convert the image to PNG instead — it will be larger, not smaller. For making files smaller, you must accept some quality loss or reduce the image dimensions.

What is the difference between TinyJPG and Squoosh?

Squoosh runs in your browser and never uploads your image to a server. TinyJPG uploads to their server, compresses it, and deletes it after an hour. Both are free for a few images per month. Squoosh is slightly more private; TinyJPG sometimes produces smaller files with the same quality.

Will reducing a JPEG to a smaller file size affect the original file?

No, as long as you save it with a different name. Always use File > Export As or Save As, not File > Save, so you keep the original untouched. This way you can try different quality settings without losing the original high-quality version.