JPEG compression trades quality for file size, and you control where that trade happens

A JPEG file shrinks when you lower its quality setting, remove unnecessary data, or resize the image itself. Unlike PNG or GIF, JPEG uses lossy compression, which means it permanently discards some image information to make the file smaller. The lower the quality number you choose, the more information gets thrown away — and the smaller the file becomes, but the blurrier or more pixelated the image looks.

Most JPEG files you encounter are already compressed to some degree. When you open one in an editing program and re-save it, you get to choose how much quality to keep. A quality setting of 80 to 85 usually looks nearly identical to the original to the human eye, while cutting file size in half. A setting of 60 to 70 looks acceptable for web use or email. Below 50, most images start to show visible damage.

The three practical ways to shrink a JPEG are: adjust the quality slider when you save, resize the image to smaller dimensions, or use a dedicated compression tool that automates the process. Which one you pick depends on what you need the image for and whether you have the original file to work from.

Key Takeaways

  • Lowering the quality setting to 75 to 85 usually cuts JPEG file size by half while keeping the image looking sharp enough for most uses.
  • Resizing an image to smaller pixel dimensions (for example, from 4000×3000 to 2000×1500) shrinks the file more dramatically than quality adjustment alone.
  • Online compression tools and desktop software can batch-process multiple JPEGs at once, explore the same quality and size settings to all of them.
  • Once you save a JPEG at a lower quality setting, that information is gone — always keep the original file if you might need a higher-quality version later.

Adjusting quality when you save the file

The simplest method is to re-save your JPEG with a lower quality setting. Open the image in any editing program — Windows Photos, Preview on Mac, Photoshop, GIMP, or even Paint — and use "Export As" or "Save As" rather than "Save" (this creates a new file instead of overwriting the original).

When the save dialog appears, look for a quality slider or quality number field. In most programs, this appears as a number from 0 to 100, or sometimes 0 to 12. A setting of 80 to 85 is the sweet spot for most photographs: the file shrinks noticeably, but the image still looks sharp. For web use or email, 75 is often acceptable. If you are archiving images you may never view again, you can go lower, but test the result first on a single image before processing a whole batch.

The exact location of this setting varies by program. In Windows Photos, export the image and the quality slider appears in the export window. In Preview on Mac, go to File > Export and adjust the quality slider before saving. In GIMP, File > Export As opens a dialog where you set the quality before clicking Export. Photoshop users should go to File > Export As, choose JPEG format, and the quality slider appears in the next dialog.

Resizing the image to smaller dimensions

A JPEG that is 4000 pixels wide takes up far more space than one that is 2000 pixels wide, even at the same quality setting. If you do not need the full resolution — for example, if the image is only going on a website or in an email — resizing first, then adjusting quality, gives you the smallest possible file.

Open the image in your editing program and look for "Resize", "Scale", or "Image Size" in the menu. Change the width or height to a smaller number; most programs will automatically scale the other dimension to keep the image from looking stretched. For web use, 1200 to 1600 pixels wide is usually enough. For email or social media, 800 to 1200 pixels is standard. For printing, you need at least 300 pixels per inch, so a 4×6 inch print needs at least 1200×1800 pixels.

After resizing, save the image as a JPEG with a quality setting of 80 to 85. The combination of smaller dimensions plus moderate quality compression typically produces a file one-quarter to one-tenth the size of the original, depending on how much you resize.

Using online or desktop compression tools

If you have many JPEGs to compress, or you want to automate the process, compression tools can batch-process entire folders at once. These tools explore the same quality and size settings to every image, which saves time if you have dozens or hundreds of files.

Online tools like TinyJPG, Compressor.io, and ImageOptim's web version let you upload JPEGs and read compressed versions without installing software. You typically upload up to 20 files at once, choose a compression level (usually labeled "low", "medium", or "high"), and read the results. These tools are free up to a certain number of images per month, then charge for additional uploads.

Desktop software like XnConvert (Windows and Mac), IrfanView (Windows), or ImageMagick (command-line, all platforms) can process entire folders of images at once. You specify the quality level, the output size in pixels, and the destination folder, then run the batch. This is faster than opening each image individually if you have 50 or more files to process.

Choosing between quality loss and file size

The trade-off between quality and size is not linear. Dropping quality from 95 to 90 might reduce file size by 10 percent. Dropping from 85 to 75 might cut it in half. Dropping from 60 to 40 might cut it in half again, but now the image looks noticeably worse. Test a single image at different quality levels to see where your threshold is.

For photographs of people, landscapes, or detailed subjects, aim for quality 80 to 85 — the loss is hard to see. For screenshots, diagrams, or images with large areas of solid color, you can often go lower (70 to 75) because these images compress better and damage is less visible. For images you are printing, never go below 80, because print magnifies compression artifacts.

If you are sending images to someone else, ask what they need. A photographer who is going to edit the image further needs quality 90 or higher. Someone viewing it on a phone or website is fine with 75 to 80. Someone archiving it for long-term storage might accept 70 if space is tight.

Keeping your original file safe

JPEG compression is permanent — once you save at a lower quality, that information is gone. You cannot open a quality-70 JPEG and re-save it at quality 95 to recover the lost detail. Always keep the original, uncompressed file (or the highest-quality JPEG you have) in a separate folder before you start compressing.

If you are working with photos from a camera or phone, the original file is usually stored in your Photos library or camera roll. Before you compress anything, copy that folder to an external drive or cloud storage as a backup. Then create a separate "compressed" or "web" folder where you save the smaller versions.

For batch processing, most tools let you specify an output folder different from the input folder, so the originals stay untouched. Use this feature — it takes one extra click and protects you from accidentally overwriting files you might need later.

When to use other formats instead

JPEG is not always the best choice for compression. If your image has large areas of solid color, sharp edges, or text, PNG or WebP often produce smaller files at the same visual quality. If you need to preserve every detail and do not care about file size, TIFF or your camera's native RAW format are lossless.

For web use, WebP is smaller than JPEG at the same quality, but not all browsers support it yet. For email or social media, JPEG is still the standard because it works everywhere. For archiving, consider whether you might edit the image later — if yes, keep the original in a lossless format and create a JPEG copy for sharing.

Frequently Asked Questions

What quality setting should I use for social media?

Quality 75 to 80 is standard for Instagram, Facebook, and Twitter. These platforms compress images again on their own servers, so going higher than 80 wastes file size. Resize to 1200 pixels wide first, then save at quality 78 for the best balance.

Can I compress a JPEG that is already been compressed?

Yes, but each time you re-save a JPEG, you lose a little more detail. If you open a quality-80 JPEG and re-save it at quality-75, the file gets smaller but the image quality drops further. Always start with the highest-quality version you have.

How much smaller will my file be if I lower quality from 85 to 75?

It varies by image content, but typically 30 to 50 percent smaller. Photographs with lots of detail compress less than images with large solid areas. Test one image at both settings to see the difference for your specific photos.

Is there a tool that compresses JPEGs without losing quality?

No tool can compress JPEG without losing quality — that is how JPEG works. Tools like ImageOptim remove unnecessary metadata (camera settings, location data) which saves a small amount of space, but the image itself stays the same. For truly lossless compression, use PNG or WebP instead.

Should I resize or adjust quality first?

Resize first, then adjust quality. Resizing removes pixels entirely, which is more efficient than compressing a large image. After resizing to your target dimensions, save at quality 80 to 85 for the smallest final file.