PNGmicro, GIFmicro and JPEGmicro are freeware Windows tools which optimise images to reduce their size.

Each program offers lossless compression by rewriting files more efficiently and stripping out surplus data, and you also get options to cut file size even further by reducing image quality.

There’s no adware, registration or other marketing hassles. The programs are portable, so download, unzip and you can use them wherever you are (at long as you’re running Windows 7 or later, anyway).

Checking the bundled files revealed that each program was using well-known open-source image optimisers, including OptiPNG and Gifsicle. If you’re an expert hoping for something new, that might be disappointing, but at least it means each tool should deliver solid and reliable results.

There are plenty of ways to tweak and reconfigure the compression process

The sleek black interface looks good, and getting started is easy. Just click the Add button and select your source images, or drag and drop them onto the program, and the files are displayed in a list.

Tapping the Options icon shows various compression settings. JPEGmicro can remove Exif and XMP tags, strip out the ICC Colour Profile, convert files to progressive or rewrite them using a lower quality level; PNGs may be interlaced, also have their colour profiles removed, or be rewritten using one of 10 lossy compression levels; and GIFs can be interlaced, have their palette reduced in size, and optionally be resized to a fixed resolution.

The programs also provide good control over the name and location of the destination files, with options to rename them, save them to a new folder, overwrite the originals, and more.

What sort of size reduction you’ll see depends very much on your source images. We used a set of files taken from regular websites, which you’d expect to be already optimised, and so it’s no surprise that the default lossless compression only saved around 1-2% on our test JPEGs and GIFs.

PNG typically gives a little more scope for lossless compression, and our test files dropped in size by around 17%. But this was very uneven, with many images remaining unchanged, and a few seeing spectacular falls, which makes it difficult to predict what a “typical” user will see.

If you can live with lossy compression, each tool offers ways to trade reduced image quality for lower file sizes. There are no great surprises here – it’s mostly about reducing the number of colours, and the standard JPEG quality setting – but the programs do at least give you plenty of control over how this works.

Exactly what you’ll save this way depends on how far you go, but there’s usually scope for improvement. Switching from lossless to lossy compression with a level of 75 cut our JPEG sizes by around 30%, without a major difference in image quality.

PNGmicro, GIFmicro and JPEGmicro don’t provide any really new take on image compression, and if you’re already using another optimisation tool then they won’t have much to offer.

The programs are well implemented, though, configurable, easy to use and no-strings free, and if you’ve not tried optimising your images before then they’re a good way to start.