How the compressor lands on an exact size
This guide explains what happens when you press Compress, how to pick a target size and format, and what to do when a result is not what you expected. All of it happens inside your browser tab.
Most compressors ask for a quality number and hand back whatever size that produces. This one works the other way round: you give it the size, and it encodes the image several times, measuring each attempt, until it finds the best version that fits.
The search starts at full resolution. It tries a range of quality settings between 45 and 97 percent and keeps the highest one that stays under your limit. If even 45 percent is too large, it does not push quality lower, because heavy block artifacts look worse than slightly fewer pixels. Instead it estimates how much smaller the image must be, scales it down by that amount, and searches again. If a scaled-down attempt fits with plenty of quality to spare, it tries a size in between to win some pixels back.
The search stops within about one and a half percent of the limit, so a 100 KB target usually gives a file of roughly 98 to 100 KB. The result card shows the quality and scale used. One kilobyte here is 1,024 bytes, and camera metadata such as GPS location is removed from every exported file.
Step by step
- Drop your images onto the page, choose them with Choose files, or paste one from the clipboard. JPG, PNG, WebP, AVIF, HEIC, TIFF, GIF, BMP, SVG, PSD and many RAW files are accepted.
- Type a target size and pick KB or MB, or tap one of the quick sizes: 20 KB, 50 KB, 100 KB, 200 KB, 500 KB or 1 MB. The default is 100 KB.
- Choose the output format: JPG, WebP or PNG. For JPG you can also pick the colour used to fill transparent areas, which is white by default.
- Optionally press Edit on a file to crop, rotate or flip it first. Cropping away empty margins is the cheapest way to keep detail at a small size.
- Press Compress. Each file shows its progress, then its new size and how much smaller it is than the original.
- Check the result with the before and after slider, then download each file on its own or use Download ZIP to save the whole batch in one go.
Output files keep their original name with the target added, so holiday.heic compressed to 50 KB is saved as holiday-50kb.jpg.
Choosing a target size
If a form or a platform states a limit, use that number, or a little less if you want a safety margin. If you are choosing for yourself, the table below gives sensible starting points. They are rules of thumb, not requirements, and you can always run the same file again with a different target.
| Job | Target to try | Why |
|---|---|---|
| Full-width image on a web page | 150–300 KB | Large enough to stay sharp on a laptop screen, small enough to load quickly on mobile data. |
| Image inside an article or listing | 50–150 KB | Displayed smaller, so fewer pixels are needed. |
| Thumbnail or avatar | 10–30 KB | Shown at a few hundred pixels at most. |
| Photos attached to an email | 300 KB–1 MB each | Keeps a message with several photos well under typical attachment limits while still printable. |
| Exam or application photo | The stated limit | For example, the SSC asks for 20–50 KB and NEET for 10–200 KB. Check the official notice for the current cycle. |
| Signature upload | The stated limit | For example, the IBPS signature limit is 10–20 KB. |
Some portals set a minimum as well as a maximum. If your result comes out below the minimum, the Increase size tool pads the file up without changing the picture.
Choosing a format
The format matters as much as the target. At the same file size, the right format can mean a noticeably sharper picture.
| Format | Best for | Transparency | How it gets smaller |
|---|---|---|---|
| JPG | Photos, and any upload form that asks for JPEG | No, transparent areas are filled with the background colour | Lower quality first, then fewer pixels |
| WebP | Web pages, and photos where you want more detail per kilobyte | Yes | Lower quality first, then fewer pixels |
| PNG | Screenshots, diagrams, logos and line art | Yes | Lossless, so only by reducing pixels |
PNG never discards detail, which is why it is the wrong choice for a photo with a tight limit: the only way to make a PNG photo smaller is to shrink it, often a lot. If a site accepts WebP, it usually gives the best result at a given size. If a form says JPEG or JPG, use JPG, because many forms check the file type.
A worked example
Here is what typically happens to a 4.2 MB phone photo of 4032 × 3024 pixels compressed to 500 KB as a JPG. The numbers are illustrative; a photo full of fine detail such as foliage or gravel needs more bytes than a portrait against a plain wall.
At full resolution, even 45 percent quality produces a file of around a megabyte, so quality alone cannot reach 500 KB. The compressor estimates that the image needs to lose a bit more than a third of its width and height, scales it to roughly 2,500 × 1,875 pixels, and searches quality again. A typical result is a file of about 490 KB at a quality somewhere around 50 percent.
That is still more pixels than a laptop screen shows at once, so it looks very close to the original. Zoom to 100 percent and fine textures are a little smoother. WebP at the same 500 KB usually keeps more texture; a 1 MB target keeps more pixels.
Batches and limits
You can compress up to 50 files at once, each up to 200 MB, on the free plan. Pro raises that to 500 files per batch and 1 GB per file, and lets the installed app work with no internet connection at all.
Each file in a batch is compressed to the same target independently, with its own quality and scale. Work runs in background workers, so the page stays responsive, and the time a large batch takes depends on your device rather than your connection.
Troubleshooting
- The result says it could not reach the target. The compressor will not shrink an image below a small fraction of its original size, so tiny limits on very detailed images can be impossible. Crop first, switch from PNG to JPG or WebP, or use a larger target if allowed.
- The result looks soft or blocky. The limit is tight for the amount of detail. Low quality on the result card means block artifacts; low scale means fewer pixels. Cropping, or WebP where accepted, helps most.
- Text in a scanned document is hard to read. Text needs pixels more than quality. Crop off the margins, capture only the part that matters, and use the largest limit allowed.
- Transparent areas turned white. JPG cannot store transparency, so transparent pixels are filled with the background colour you choose. Pick WebP or PNG to keep transparency.
- A HEIC photo from an iPhone. HEIC files are decoded in your browser and saved as JPG, WebP or PNG, since most forms do not accept HEIC. Decoding takes a little longer than for a JPG.
- The file came back unchanged. An image already under the target in the chosen format is passed through, minus its metadata. Pick a smaller target or another format to force a new encode.
- WebP shows an error. A few older browsers cannot create WebP files. Use JPG, or update the browser.
- A portal still rejects the file. Check the format, the pixel dimensions and any minimum size the form asks for, not only the maximum. Some systems count a kilobyte as 1,000 bytes rather than 1,024, so if a file is rejected right at the limit, set a target a couple of KB lower.
Compressing in the browser versus uploading
Many compressors send your file to a server and send the result back. That works on any device and can be quick on a good connection, but a copy of your photo, passport scan or signature then sits on someone else's computer, under whatever retention policy that service has.
Here the file never leaves your device. There is no upload to wait for, which matters with large originals or a slow connection. The trade-off is that speed depends on your hardware, so a big batch on an old phone is slower than on a laptop. The work itself needs no network, and with Pro the installed app runs fully offline.