Compress JPG, PNG, WebP, AVIF and HEIC without uploading anything. PNG comes out losslessly compressed, transparency is left alone, and you never get back a file larger than the one you started with.
Quick answer: Drop your images into the Convertlo image compressor and download them. PNGs are recompressed losslessly, JPEGs use a quality you control, transparency is preserved, and everything runs in your browser — nothing is uploaded.
Compress your images now Batch · every format · nothing uploaded
Compression is not one thing — it depends on your format
Most compressors treat every image the same way and quietly convert your PNG to a lossy format to claim a bigger percentage. That is not compression, it is a format change, and it is why a logo comes back with fuzzy edges. Here is what actually happens to each format:
Format
What we do
Quality cost
PNG
Re-encode losslessly with a better encoder
None — pixels are identical
JPEG
Quality sweep, capped at 82
You choose it
WebP
Quality sweep, alpha kept
You choose it
HEIC
Decoded, then compressed as JPEG
You choose it
What lossless PNG compression is worth
A browser's built-in PNG encoder is generic: it picks one row filter and one deflate setting and moves on. A dedicated encoder searches for the best filter per row before compressing, which finds real savings in exactly the images people compress most — screenshots and UI captures, where large areas repeat.
A concrete example we measured: a 224.5 KB Android screenshot came out at 155.8 KB, a saving of 30.6%, with every single byte of pixel data identical after decoding it back. No quality setting was involved because none is possible — the image is unchanged, only the encoding is better.
Two guarantees worth knowing about
An empty pixel stays empty. Transparency is never filled with white and never with black. If your image really has an alpha channel and you have not picked a format yourself, the output stays in a format that can store it, so a logo on a transparent background comes back exactly that way.
You never get a bigger file. Some images are already optimised — a palette PNG, a screenshot, a photo that has already been through a good encoder. When nothing we produce beats the original, the honest answer is your original file, returned untouched, and the result says so rather than quietly handing you something larger.
Frequently Asked Questions
JPG and JPEG, PNG, WebP, AVIF where your browser supports it, and HEIC from an iPhone. The compressor keeps your format by default and only changes it if you pick a different one yourself.
It depends on the format. PNG is compressed losslessly, so the pixels that come out are identical to the ones that went in. JPEG and WebP are lossy formats where the quality setting decides how much detail is spent; around 75 to 82 is where the file shrinks sharply while the picture still looks untouched.
It is preserved. An empty pixel stays empty — transparency is never filled with white or black. If an image has real transparency and you have not chosen a format yourself, the output stays in a format that can store it.
Not by accident. If nothing we produce beats your original file, you get the original back untouched and the result reports no change. The only exceptions are ones you asked for: an explicit resize, a target file size, or picking a different output format.
No. Everything runs in your browser using WebAssembly and canvas, so images never leave your device. That makes it safe for documents, screenshots, ID photos and anything else you would not want on someone else's server.
There is no account limit and no queue. You can drop in a batch and the work happens on your own machine, so the practical ceiling is your device's memory rather than a plan tier.