A free alternative to TinyPNG for compressing images

TinyPNG popularized something genuinely useful: shrinking a PNG or a JPG with almost no visible loss of quality. It works well and we have no complaints about it. But its free web version comes with conditions —a cap on images and size, and paid advanced features— and, like almost every online compressor, it uploads your images to its server to process them.

This guide explains, with concrete numbers, where those limits are, and presents an alternative that is free, unlimited and uploads nothing: it compresses inside your browser with the same professional codecs desktop tools use.

What TinyPNG limits in its free version

It is not that it does not work for free; it is that the unpaid version has caps. As of this guide, on its website:

• Up to 20 images per batch and a maximum of 5 MB per image. If you have a folder of phone photos (which easily exceed 5 MB) or a large batch, you are stuck doing it in rounds or left out.
• Unlimited compression is paid (Web Pro / Web Ultra plans). For real volume —or to automate it— you need the developer API, billed per image.
• Resizing and cropping are reserved for the paid API.
• Format conversion on the free web is limited to a few images.

To be fair and not overstate it: TinyPNG does not add a watermark and does not force you to sign up for the basics. The real friction is elsewhere: usage caps and, above all, having to upload each image to someone else's server. For internal screenshots, unpublished product photos or client images, uploading them to a third party is not always acceptable.

The alternative: compress in the browser, free and without uploading

Colibrí's Compress image tackles exactly that. It is free, with no sign-up, no watermark and no limit on number or size, because there is no server: everything happens inside your browser, using your own device's power. Your images are never uploaded anywhere, and the EXIF metadata (including GPS location) is stripped along the way.

You can drop as many images as you want, of any size, compress them with the same settings and download them one by one or all together in a ZIP.

The same professional codecs

The key is that it does not use the browser's basic compression, but the same codecs as serious tools, compiled to WebAssembly to run locally:

• MozJPEG for JPEG: squeezes noticeably more than the browser's "Save as" at the same quality.
• libwebp for WebP and AOM for AVIF: modern formats that, at the same quality, weigh far less than a JPG or a PNG and keep transparency.
• OxiPNG for PNG: lossless optimization (the image stays identical, just lighter).

AVIF deserves a special mention: it is the format that compresses the most today, and the browser cannot generate it on its own. Here you get it free and unlimited, whereas on most websites it is a paid or limited feature.

Lossy vs lossless PNG: the honest difference

Here it pays to be transparent. TinyPNG compresses PNG with loss: it reduces the color palette so the file weighs much less, keeping the PNG format. Colibrí optimizes PNG losslessly with OxiPNG, so the image stays identical but the saving on a given PNG is smaller than that quantization.

Does that mean TinyPNG "wins" on PNG? Not necessarily, and this is the interesting part: if your goal is the smallest possible size, converting that PNG to WebP or AVIF —which Colibrí does, for free— usually yields an even smaller file than the quantized PNG, with the same visual quality and keeping transparency. Only if you must keep the PNG format with maximum reduction does lossy quantization have the edge in that specific case.

In short: to really cut weight, choose WebP or AVIF; to keep the exact PNG, use "Keep" and you get an identical, lighter PNG.

Step by step

1. Open Compress image and drag your photos (or click to pick them). They open in your browser; nothing is uploaded.
2. Choose the output format: "Keep" preserves each image's format; WebP or AVIF achieve the smallest size.
3. Adjust the quality and, if you like, a maximum width or height (reducing the dimensions is the most effective way to save weight).
4. Press Compress, check how much each image saves and download them one by one or in a ZIP.

If you also want to convert between formats or generate your site's favicon, the rest of the toolbox is right there, and they all work the same way: in your browser, nothing uploaded.