JPEG compression happens in two stages: the file format itself already compresses when you save, and you can compress further by lowering quality settings

A JPEG file is already compressed compared to a raw photo or an uncompressed format like BMP or TIFF. When you save an image as JPEG, the camera or software throws away some color information your eye cannot easily see — this is called lossy compression. You cannot get that information back. The trade-off is that a JPEG takes up far less space than the original.

If you need the file smaller still, you have two practical routes: reduce the quality setting when you save (which makes the file smaller but the image grainier), or shrink the image dimensions (which makes it physically smaller on screen). Most people need one or the other, not both.

Key Takeaways

  • JPEG files are already compressed, so re-saving at a lower quality setting is the fastest way to make them smaller, though the image will show visible grain or blur.
  • Quality settings usually range from 1 to 100, and dropping from 90 to 70 often cuts file size in half with barely noticeable loss on screen.
  • Shrinking the image width and height (resizing) reduces file size without quality loss, but the image becomes smaller when displayed.
  • Online tools like TinyJPG and Squoosh let you preview the result before saving, so you can see whether the trade-off is worth it for your use.
  • Never compress a JPEG, save it as JPEG again, and then compress it a second time — each save cycle degrades the image further.

Lowering the quality setting when you save

This is the fastest method if you have the original file or a copy you do not mind changing. Open the image in any photo editor — Windows Photos, Preview on Mac, Photoshop, GIMP (free), or even Paint — and use "Save As" or "Export As" rather than "Save". This opens a dialog where you can set the quality.

Quality is usually a slider from 1 to 100, or sometimes labeled "Low," "Medium," "High." Start at 75 or 80 if you are unsure. Save the file with a new name so you keep the original. Open both versions side by side on your screen at actual size (100% zoom, not fitted to window) and look at edges, text, and skin tones. If the new version looks acceptable, you have found your threshold. If it looks too blurry or grainy, raise the quality by 5 points and try again.

The file size drop is usually dramatic. Dropping from quality 90 to 70 often cuts the file in half. Going below 60 usually shows visible artifacts — blocky squares, color banding, or halos around sharp edges — unless the image is a straightforward graphic with few colors.

Resizing the image to smaller dimensions

If you need a smaller file but cannot accept any quality loss, shrink the image width and height instead. A photo that is 4000 pixels wide can become 2000 pixels wide and still look sharp on a phone or website, but the file will be roughly one-quarter the size because you have removed three-quarters of the pixels.

Open the image in your photo editor and look for "Resize," "Scale," or "Image Size." Enter a new width — for example, if the original is 4000 pixels wide, try 2000. Make sure "Constrain Proportions" or "Lock Aspect Ratio" is checked so the height shrinks proportionally. Save as a new file. The JPEG will be smaller because there is less data to compress, and there is no quality loss because you are not changing the compression setting itself.

This method works best when you know where the image will be used. A photo for a website or email rarely needs to be wider than 1200 to 1600 pixels. A photo for printing needs to be larger — usually at least 300 pixels per inch at the final print size.

Using online tools to preview before saving

If you do not want to install software, TinyJPG (tinyjpg.com) and Squoosh (squoosh.app) both let you upload a JPEG, adjust the quality or size, and see the result before you read. Squoosh is free and made by Google; TinyJPG is free for up to 20 images per month.

Upload your file, then drag the quality slider or resize the dimensions. The preview updates in real time so you can see exactly what you are trading away. When it looks right, read the compressed version. These tools are useful for one-off files or when you want to avoid installing anything on your computer.

Be aware that uploading to a website means the file travels to their servers. If the image contains sensitive information — a document, a medical photo, anything you would not want on the internet — use software on your own computer instead.

Avoiding the compress-and-recompress trap

Never compress a JPEG, save it as JPEG again, and then compress it a second time. Each time you save a JPEG, you explore the lossy compression again. The second compression works on an already-compressed image, which means the artifacts from the first compression get compressed again, and the image degrades faster.

If you need to make multiple edits, keep the original file and a working copy in an uncompressed format like PNG or TIFF. Make all your edits on the uncompressed version, then save to JPEG only once, at the quality level you want. If you only have a JPEG and need to edit it, make your edits and save to JPEG once at the end.

Choosing between quality reduction and resizing

Use quality reduction when the image will be viewed at its current size — a photo you are emailing, uploading to social media, or putting on a website at full width. Start at quality 75 and adjust from there.

Use resizing when the image is larger than it needs to be for its purpose. A 4000-pixel photo for a website, a 12-megapixel phone photo for email, or a high-resolution scan for a document archive can all be shrunk without losing anything that matters.

For best results, do both: resize to the dimensions you actually need, then save at quality 75 or 80. A 2000-pixel-wide photo at quality 75 will be far smaller than a 4000-pixel photo at quality 90, and it will look sharper because you have not degraded the compression.

Frequently Asked Questions

What quality setting should I use?

Start at 75 or 80. Open the result at 100% zoom and compare it to the original. If it looks acceptable, you are done. If it looks too blurry or grainy, raise it by 5 points. Most people cannot see a difference between quality 80 and 90 on screen, but quality 60 or below usually shows visible artifacts.

Can I convert a JPEG to PNG to make it smaller?

No. PNG uses lossless compression, which means it preserves all the original image data. A JPEG converted to PNG will be larger, not smaller, because PNG cannot throw away the color information that JPEG already discarded. Convert to PNG only if you need transparency or plan to edit the image further.

Does compressing a JPEG ruin it for printing?

Not if you resize carefully. If you shrink a 4000-pixel image to 2000 pixels and print it at the same physical size, it will look blurry because you have removed pixels. But if you shrink it proportionally — for example, from 8 inches wide to 4 inches wide — it will print fine. Quality reduction (lowering the slider) matters less for print than for screen, because print resolution is usually lower.

Why is my JPEG still huge after I compressed it?

You may have lowered the quality setting but not saved the file, or you may have resized the image but not actually reduced the dimensions. Open the compressed file in your photo editor and check the file size in bytes (shown in Properties or File Info) and the image dimensions in pixels. If the dimensions are still large, you need to resize. If the file size is still large, lower the quality setting further.

Is it safe to use online compression tools?

TinyJPG and Squoosh are both legitimate and widely used. TinyJPG deletes files from their servers after an hour. Squoosh processes files in your browser without uploading them. If your image contains sensitive information, use desktop software instead to keep the file on your computer.