Convert an image

Turn a PNG screenshot into a lightweight WebP, get a JPEG out of an AVIF that your software refuses to open, or move to a lossless PNG when you need exact pixels. Each format has a job it is genuinely good at, and this tool moves your image between them with encoder settings chosen for that format.

How to use it

1. Open the Convert Image tool and drop in your file.
2. Choose the output format — JPEG, PNG, WebP or AVIF.
3. Optionally set a quality between 1 and 100 (82 is a good default).
4. Convert, then download the result.

Which format should you actually pick?

The honest answer depends on what is in the image and where it is going. This is the short version:

JPEG	Photographs going somewhere old or unpredictable. Universally supported, no transparency, and it degrades gracefully at moderate quality.
PNG	Screenshots, diagrams, logos and anything with flat colour, sharp edges or transparency. Lossless, so text stays perfectly crisp — but heavy for photographs.
WebP	The sensible default for the web today. Roughly 25–35% smaller than an equivalent JPEG, supports transparency, and is supported by every current browser.
AVIF	The smallest of the four by a wide margin, often half the size of WebP at the same visual quality. Slower to encode and not yet universal outside browsers.

Lossy and lossless are not interchangeable

JPEG, WebP and AVIF are lossy: they achieve their size by discarding detail the eye is unlikely to miss. PNG is lossless: it reproduces the original pixels exactly. That distinction matters most for images with hard edges — a screenshot of text saved as a JPEG picks up faint smudges around every letter, which is why screenshots belong in PNG or WebP.

It also means conversions are not symmetric. Going from PNG to JPEG throws detail away permanently; converting the result back to PNG cannot recover it, it only stops any further loss. Always convert from the best original you have rather than from something already compressed.

What the quality number does

For the lossy formats, quality is a dial between file size and fidelity. Around 82 is a good general default — visually indistinguishable from the original at normal viewing size for most photographs. Dropping to 60 makes a noticeably smaller file with artefacts that start to show in smooth gradients like skies. Above 90 the returns diminish sharply: the file grows quickly while the visible improvement is close to nothing.

The number is not comparable between formats. AVIF's scale is more aggressive than JPEG's, so slimdocs adjusts it for you — the same setting produces a broadly similar result rather than an unexpectedly mangled AVIF. Quality has no effect at all when the output is PNG, since PNG does not discard anything.

Transparency and how it is handled

PNG, WebP and AVIF can all store a transparent background. JPEG cannot — the format simply has no channel for it. Converting a transparent PNG to JPEG therefore has to decide what to put behind the image, and a naive converter often leaves it black, producing an unpleasant surprise around a logo.

slimdocs flattens transparency onto white when the target is JPEG, which is almost always what was intended. If you need the transparency preserved, choose WebP or PNG instead.

Converting is not the same as compressing

This tool changes the container and codec at a quality you choose. The compressor is the tool to reach for when your goal is purely a smaller file and you want slimdocs to pick sensible settings for you across PDFs, images and Office documents alike.

For the biggest saving on a photo, combine the two ideas: resize it to the dimensions you actually need first, then convert to WebP or AVIF. Each step multiplies the last, and the result is routinely a small fraction of what you started with.