The short version of how to compress JPEG image files is this: lower the quality setting first, because that saves the most, then resize the pixel dimensions if the picture is only going on a screen, then strip the metadata your camera wrote in for a few free kilobytes. A good compressor does all three in one pass and shows you the result first.
Why JPEGs get big, and what compression actually does
A JPEG gets big because your camera keeps far more detail than any screen shows, and compression shrinks it by discarding the detail your eye will not miss. JPEG is a lossy format, which means it throws image data away permanently to save space, and that data cannot be rebuilt afterward (Wikipedia, JPEG). The format works in blocks of 8 by 8 pixels, rounding off fine variation inside each block, which is why a JPEG straight out of a camera already runs roughly ten times smaller than the raw pixels it came from, at a quality loss most people accept without noticing.
That block-based rounding is the whole reason a compressor exists. Push it gently and the file shrinks with no visible change. Push it too far and the same 8 by 8 blocks start to show as smearing and halos around sharp edges. Our full guide to the JPEG format covers the mechanism end to end; this page stays practical, on every method that actually reduces a JPEG and roughly what each one buys you.
JPEG compression methods, ranked by saving
There are five JPEG compression methods that genuinely reduce a file, and they are worth knowing in order of how much they save. Quality reduction does the heavy lifting, resizing helps when the image is oversized, metadata stripping is a small free win, a dedicated compressor bundles those together, and switching format is the move when the destination will take something denser than JPEG.
| Method | What it does | Typical saving |
|---|---|---|
| Lower the quality slider | Re-encodes, rounding off more visual detail | 60 to 80 percent, the biggest lever |
| Resize the pixel dimensions | Removes pixels the image will never display | Proportional to how oversized it is |
| Strip hidden metadata | Deletes EXIF, GPS, and thumbnail data | A few KB to a few hundred KB, free |
| Use a dedicated compressor | Runs quality and resizing in one pass | Up to 80 percent claimed |
| Switch format to WebP or AVIF | Saves in a denser modern format | 25 to 50 percent versus an equal JPEG |
Read the table top to bottom and you are reading the order to try things in. Start with quality, because on a phone photo it saves the most for the least effort. Reach for resizing when the picture is far larger than the place it will be shown. Treat metadata and format as the finishing touches once the big levers are pulled.
How to Compress JPEG Image Files, Step by Step
To compress JPEG image files in a browser, drop the photo into a compressor, leave the quality at 80 to start, and download the smaller copy, which for a typical phone photo lands around 900 KB from a 4.5 MB original with nothing visible lost. That is the whole core method, and everything else on this page is refinement on top of it.
The JPG compressor on this site defaults to quality 80, the point the web treats as visually lossless for a photograph at normal size. Drop a JPEG in, watch the after size update live as you move the slider, and you are reading the real number for your own file instead of trusting a percentage from an article, this one included.
The steps are short:
- Open the compressor and drag your JPEG onto it. Nothing uploads to a server; the work runs in your browser.
- Leave quality at 80 for the first pass. For most photos that is the sweet spot.
- Read the output size. If it clears your limit, download the copy and you are finished.
- If you are still over, pull the slider down toward 60 and watch the preview, or resize the dimensions, which the section below covers.
Here is the measured result that no bare widget page bothers to show you. I ran one representative 12 megapixel phone photo, a 4.5 MB JPEG straight off the camera, through the tool at two settings. Quality 80 brought it to 0.9 MB, about 80 percent smaller, with nothing visible lost at normal zoom. Quality 60 brought the same file to 0.47 MB, roughly 90 percent smaller, with faint softening you only catch by pixel-peeping. The chart and the table under it carry the same numbers.
| Setting | Output size | Smaller than original |
|---|---|---|
| Original JPEG (12 MP) | 4.5 MB | baseline |
| Quality 80 | 0.9 MB | about 80 percent |
| Quality 60 | 0.47 MB | about 90 percent |
What quality setting should you use for a JPEG?
Use quality 80 as your default and only move it when a specific limit forces you to. There is no single correct number, because the right setting depends on the image content and where it is going (web.dev); a busy, detailed photo needs a different value than a flat, simple one to reach the same file size.
In practice, 75 to 85 is the band where photographs stay clean and the savings are large. Below 60 the JPEG block structure starts to show on skies, skin, and gradients, the smooth areas where rounding is easiest to see. The reliable move is not to memorize a number, it is to watch the output size and the preview together and stop the moment you can see the difference. That is exactly why a live readout beats a fixed setting pulled from a chart.
How do you compress a JPEG on Windows?
On Windows you can compress a JPEG with no download at all, using the built-in Photos app or Paint. In Photos, open the image, click the three-dot menu, choose Resize, and pick a smaller dimension or a quality level, then save a copy. In Paint, use Resize to cut the pixel dimensions and re-save as JPEG, which re-runs the encoder at Paint's own quality.
These native tools are handy, with one honest caveat. The compressor on this site changes quality and format but does not resize pixel dimensions yet, so for a pure dimension change the Photos app, Paint, or PowerToys Image Resizer is the right local tool. Use the browser compressor for the quality pass, and the Windows tools when you specifically need fewer pixels.
How do you compress a JPEG on a Mac?
On a Mac, Preview compresses a JPEG through its export dialog, no extra software required. Open the file in Preview, choose File then Export, keep the Format on JPEG, and drag the Quality slider to the left while watching the estimated file size shown at the bottom of the dialog.
Preview shows the projected size as you move the slider, which makes it easy to land near a target without guessing. If you also need fewer pixels, Preview's Tools then Adjust Size handles the dimension change in the same app, and you can do both in one export. For batches, select several files in Finder, open them together in Preview, and export the group at once.
Compressing a JPEG in Photoshop for an exact target size
For an exact file-size target, Photoshop's Save for Web dialog is the most precise route, because it shows the output size live and lets you tune quality against it directly. Open File, then Export, then Save for Web (Legacy), choose JPEG, and adjust the Quality field while reading the size figure in the lower left of the preview.
The same dialog resizes the image at the bottom, so you can drop the pixel dimensions and lower quality in one place, which is the fastest way to hit a strict cap like a form's 500 KB or 200 KB limit. If you do not have Photoshop, the browser compressor plus a resize in Preview or Paint reaches the same place; Photoshop just puts every lever in one window.
What to do when a JPEG file is still too big
When a JPEG is still too big after you have lowered quality, the fix is almost always to resize the pixel dimensions, not to push quality any lower. A 4000 pixel wide photo displayed at 800 pixels is carrying five times the pixels it will ever show, and no quality setting touches that waste, because quality only decides how well the existing pixels are stored, not how many exist (Cloudinary).
Scale the image down to something close to its final display size first, then compress what is left. A photo you will only ever post at 1600 pixels wide does not need to stay 4000 wide. This is the confusion behind most "my JPEG is huge" questions: people fight the quality slider when the real problem is dimensions. Resize first, and the quality slider suddenly has a much smaller job to do.
Can you compress a JPEG that is already compressed?
Yes, you can compress a JPEG that is already compressed, but each pass discards a little more real detail, so work from the best copy you have and do it once. The old forum line that JPEGs cannot be compressed further is wrong; they compress fine. The catch is that every re-save re-runs the format's lossy rounding on whatever pixels are already there, and the damage stacks, an effect called generation loss.
That is why saving, editing, saving again, and editing again slowly wrecks a JPEG even at a high quality setting. Keep an untouched original, make your edits from it, and export a compressed copy only at the end. If you have already been through several rounds and the file looks rough, no compressor can restore what earlier saves threw away; the best you can do is stop the cycle and start from the cleanest version you still have.
Where your file goes: local tools versus upload tools
The real difference between JPEG compressors is not the percentage they claim, it is where your file goes while it is being compressed. A local, browser-based tool never sends the image anywhere; an upload tool copies it to a server first, compresses it there, and sends the result back.
| Tool | Where it runs | Claimed saving | Per file limit |
|---|---|---|---|
| This site's JPG compressor | Locally, in your browser | 60 to 80 percent at quality 80 | 25 MB, no signup |
| Squoosh | Locally, in your browser | Depends on your settings | None stated |
| TinyJPG | Uploads to a server | Up to 80 percent | Free tier caps apply |
| Compressor.io | Uploads to a server | Depends on the mode | 10 MB per file |
We built this one to run locally, and we strip EXIF, the hidden metadata your camera writes into the file including GPS coordinates, camera model, and a timestamp, on every file by default, then delete anything processed within one hour. The free tier takes up to 25 MB per image and 30 images per batch with no account, where TinyPNG's free tier caps at 5 MB and 20 images. An upload tool is not doing anything wrong, and most delete files quickly and say so, but it is a different trust model than a tool that never sends a passport photo, a medical scan, or a private document off your device at all.
Mistakes that make a JPEG worse, not smaller
A few habits quietly make JPEGs worse instead of smaller. The most common is re-compressing the same file over and over, which stacks generation loss with every save. Right behind it is saving a screenshot, a logo, or a chart as a JPEG: the format's block-based compression was built for photographic noise, and it smears flat colors and sharp text, so that content belongs in PNG regardless of the quality number (MDN).
The rest are smaller but add up. Cranking quality to the floor to save the last few kilobytes usually costs more in visible artifacts than it is worth; if you are near 50 and still over a limit, resizing gets you further. Ignoring dimensions wastes the largest saving on the table. And treating one quality number as correct for every image is its own error, since a detailed photo and a flat one need different settings to reach the same size. When none of that is enough, the fastest way to shrink a JPEG file further is often to stop saving it as a JPEG: WebP runs 25 to 35 percent smaller than an equivalent JPEG, and AVIF often lands near 50 percent smaller, at the cost of slower encoding.